Related
I need to remove similar duplicates as well as real duplicates from 2D array in JavaScript.
let a = [
[5, 6],
[1,1],
[6,5],
[1,1],
[3,2],
[2,3]
]
function makeUnique(arr) {
var uniques = [];
var itemsFound = {};
for(var i = 0, l = arr.length; i < l; i++) {
var stringified = JSON.stringify(arr[i]);
if(itemsFound[stringified]) continue;
uniques.push(arr[i]);
itemsFound[stringified] = true;
}
return uniques;
}
a=makeUnique(a)
console.log(a);
I have got this output:
[ [ 5, 6 ], [ 1, 1 ], [ 6, 5 ], [ 3, 2 ], [ 2, 3 ] ]
Correct should be:
[ [ 5, 6 ], [ 1, 1 ], [ 2, 3 ] ]
My code removes correctly duplicates, but I need to remove similar duplicates also.
For example if I have [3,2] and [2,3] I should remove [3,2] (the one which has bigger starting index value.)
Could you help me to fix this?
Here is an example of how you can do it:
function makeUnique(arr) {
var uniques = [];
var itemsFound = {};
arr.sort((a, b) => a[0] + a[1] - (b[0] + b[1]))
for (var i = 0, l = arr.length; i < l; i++) {
if (!itemsFound[arr[i]] && !itemsFound[[arr[i][1], arr[i][1]]]) {
uniques.push(arr[i]);
itemsFound[arr[i]] = true;
itemsFound[[arr[i][1], arr[i][0]]] = true;
}
}
return uniques;
}
I hope it helps.
There are two parts
similar should be considered
among similar, one with smaller first key should stay
1. Similar should be considered
Here you can just make the key for hashmap in such a way that similar items produce same key.
One way to do that is sort the items in the tuple and then form the key, as there are two items only, first one will be min and second one will be max
let a = [
[5, 6],
[1,1],
[6,5],
[1,1],
[3,2],
[2,3]
]
function makeUnique(arr) {
var uniques = [];
var itemsFound = {};
for(var i = 0, l = arr.length; i < l; i++) {
let [a,b] = arr[i];
const hashKey = [ Math.min(a,b), Math.max(a,b)];
var stringified = JSON.stringify(hashKey);
if(itemsFound[stringified]) continue;
uniques.push(arr[i]);
itemsFound[stringified] = true;
}
return uniques;
}
let ans1=makeUnique(a)
console.log(ans1);
2. Among similar, the one with smaller first key should stay
Now you can remember in the hashmap what the value for a key was and keep updating it based on the correct candidate
let a = [
[5, 6],
[1,1],
[6,5],
[1,1],
[3,2],
[2,3]
]
function makeUniqueSmallerFirst(arr) {
var items = {};
for(var i = 0, l = arr.length; i < l; i++) {
let [a,b] = arr[i];
const hashKey = [ Math.min(a,b), Math.max(a,b)];
var stringified = JSON.stringify(hashKey);
if (stringified in items) {
let previous = items[stringified];
if (previous[0] > arr[i][0]) {
items[stringified] = arr[i];
}
} else {
items[stringified] = arr[i] // I am just storing the array because if I see a similar item next time, I can compare if that has first item smaller or not
}
}
return Object.values(items); // this doesn't guarantee output order though
// if you want order as well . you can iterate over input array once more and arrange the items in the preferred order.
}
let ans2=makeUniqueSmallerFirst(a)
console.log(ans2);
UPDATED (More simple and faster example for ES5+):
function makeUnique(arr) {
return new Set(a.map(
arr => JSON.stringify(arr.sort((a, b) => a - b)))
)
}
const m = makeUnique(a)
console.log(m) //
OLD:
This is an example of code that makes a two-dimensional array with arrays of any length unique.
let a = [
[5, 6],
[1, 1],
[6, 5],
[1, 5],
[3, 2],
[2, 3],
[6, 5, 3],
[3, 5, 6]
]
function isUnique(uniqueArray, checkedArray) {
let checked = [...checkedArray];
let unique = [...uniqueArray];
let uniqueValue = 0;
unique.forEach(value => {
if (checked.includes(value)) {
checked.splice(checked.indexOf(value), 1)
} else uniqueValue++;
})
return uniqueValue > 0;
}
function makeUnique(array2d) {
let unique = [array2d[0]]
array2d.forEach(checkedArray => {
if (unique.some(uniqueArray => {
if (checkedArray.length !== uniqueArray.length) return false;
return !isUnique(uniqueArray, checkedArray)
}
)) return 0;
else unique.push(checkedArray)
})
return unique
}
console.log(makeUnique(a)) // [ [ 5, 6 ], [ 1, 1 ], [ 1, 5 ], [ 3, 2 ], [ 6, 5, 3 ] ]
isUnique() this function checks if the numbers in both arrays are unique, and if they are, it outputs true. We use the copy through spread operator, so that when you delete a number from an array, the array from outside is not affected.
makeUnique() function makes the array unique, in the following way:
It checks if our unique two-dimensional array has at least one array that is identical to checkedArray
The first check if the arrays are of different lengths - they are unique, skip and check for uniqueness, if !isUnique gives out true, then the array is skipped by return 0
This question's answers are a community effort. Edit existing answers to improve this post. It is not currently accepting new answers or interactions.
How do I append an object (such as a string or number) to an array in JavaScript?
Use the Array.prototype.push method to append values to the end of an array:
// initialize array
var arr = [
"Hi",
"Hello",
"Bonjour"
];
// append new value to the array
arr.push("Hola");
console.log(arr);
You can use the push() function to append more than one value to an array in a single call:
// initialize array
var arr = ["Hi", "Hello", "Bonjour", "Hola"];
// append multiple values to the array
arr.push("Salut", "Hey");
// display all values
for (var i = 0; i < arr.length; i++) {
console.log(arr[i]);
}
Update
If you want to add the items of one array to another array, you can use firstArray.concat(secondArray):
var arr = [
"apple",
"banana",
"cherry"
];
// Do not forget to assign the result as, unlike push, concat does not change the existing array
arr = arr.concat([
"dragonfruit",
"elderberry",
"fig"
]);
console.log(arr);
Update
Just an addition to this answer if you want to prepend any value to the start of an array (i.e. first index) then you can use Array.prototype.unshift for this purpose.
var arr = [1, 2, 3];
arr.unshift(0);
console.log(arr);
It also supports appending multiple values at once just like push.
Update
Another way with ES6 syntax is to return a new array with the spread syntax. This leaves the original array unchanged, but returns a new array with new items appended, compliant with the spirit of functional programming.
const arr = [
"Hi",
"Hello",
"Bonjour",
];
const newArr = [
...arr,
"Salut",
];
console.log(newArr);
If you're only appending a single variable, then push() works just fine. If you need to append another array, use concat():
var ar1 = [1, 2, 3];
var ar2 = [4, 5, 6];
var ar3 = ar1.concat(ar2);
alert(ar1);
alert(ar2);
alert(ar3);
The concat does not affect ar1 and ar2 unless reassigned, for example:
var ar1 = [1, 2, 3];
var ar2 = [4, 5, 6];
ar1 = ar1.concat(ar2);
alert(ar1);
There is a lot of great information on JavaScript Reference.
Some quick benchmarking (each test = 500k appended elements and the results are averages of multiple runs) showed the following:
Firefox 3.6 (Mac):
Small arrays: arr[arr.length] = b is faster (300ms vs. 800ms)
Large arrays: arr.push(b) is faster (500ms vs. 900ms)
Safari 5.0 (Mac):
Small arrays: arr[arr.length] = b is faster (90ms vs. 115ms)
Large arrays: arr[arr.length] = b is faster (160ms vs. 185ms)
Google Chrome 6.0 (Mac):
Small arrays: No significant difference (and Chrome is FAST! Only ~38ms !!)
Large arrays: No significant difference (160ms)
I like the arr.push() syntax better, but I think I'd be better off with the arr[arr.length] Version, at least in raw speed. I'd love to see the results of an IE run though.
My benchmarking loops:
function arrpush_small() {
var arr1 = [];
for (a = 0; a < 100; a++)
{
arr1 = [];
for (i = 0; i < 5000; i++)
{
arr1.push('elem' + i);
}
}
}
function arrlen_small() {
var arr2 = [];
for (b = 0; b < 100; b++)
{
arr2 = [];
for (j = 0; j < 5000; j++)
{
arr2[arr2.length] = 'elem' + j;
}
}
}
function arrpush_large() {
var arr1 = [];
for (i = 0; i < 500000; i++)
{
arr1.push('elem' + i);
}
}
function arrlen_large() {
var arr2 = [];
for (j = 0; j < 500000; j++)
{
arr2[arr2.length] = 'elem' + j;
}
}
I think it's worth mentioning that push can be called with multiple arguments, which will be appended to the array in order. For example:
var arr = ['first'];
arr.push('second', 'third');
console.log(arr);
As a result of this you can use push.apply to append an array to another array like so:
var arr = ['first'];
arr.push('second', 'third');
arr.push.apply(arr, ['forth', 'fifth']);
console.log(arr);
Annotated ES5 has more info on exactly what push and apply do.
2016 update: with spread, you don't need that apply anymore, like:
var arr = ['first'];
arr.push('second', 'third');
arr.push(...['fourth', 'fifth']);
console.log(arr) ;
You can use the push and apply functions to append two arrays.
var array1 = [11, 32, 75];
var array2 = [99, 67, 34];
Array.prototype.push.apply(array1, array2);
console.log(array1);
It will append array2 to array1. Now array1 contains [11, 32, 75, 99, 67, 34].
This code is much simpler than writing for loops to copy each and every items in the array.
With the new ES6 spread operator, joining two arrays using push becomes even easier:
var arr = [1, 2, 3, 4, 5];
var arr2 = [6, 7, 8, 9, 10];
arr.push(...arr2);
console.log(arr);
This adds the contents of arr2 onto the end of arr.
Babel REPL Example
If arr is an array, and val is the value you wish to add use:
arr.push(val);
E.g.
var arr = ['a', 'b', 'c'];
arr.push('d');
console.log(arr);
Use concat:
a = [1, 2, 3];
b = [3, 4, 5];
a = a.concat(b);
console.log(a);
JavaScript with the ECMAScript 5 (ES5) standard which is supported by most browsers now, you can use apply() to append array1 to array2.
var array1 = [3, 4, 5];
var array2 = [1, 2];
Array.prototype.push.apply(array2, array1);
console.log(array2); // [1, 2, 3, 4, 5]
JavaScript with ECMAScript 6 (ES6) standard which is supported by Chrome, Firefox, Internet Explorer, and Edge, you can use the spread operator:
"use strict";
let array1 = [3, 4, 5];
let array2 = [1, 2];
array2.push(...array1);
console.log(array2); // [1, 2, 3, 4, 5]
The spread operator will replace array2.push(...array1); with array2.push(3, 4, 5); when the browser is thinking the logic.
Bonus point
If you'd like to create another variable to store all the items from both arrays, you can do this:
ES5 var combinedArray = array1.concat(array2);
ES6 const combinedArray = [...array1, ...array2]
The spread operator (...) is to spread out all items from a collection.
If you want to append two arrays -
var a = ['a', 'b'];
var b = ['c', 'd'];
then you could use:
var c = a.concat(b);
And if you want to add record g to array (var a=[]) then you could use:
a.push('g');
There are a couple of ways to append an array in JavaScript:
1) The push() method adds one or more elements to the end of an array and returns the new length of the array.
var a = [1, 2, 3];
a.push(4, 5);
console.log(a);
Output:
[1, 2, 3, 4, 5]
2) The unshift() method adds one or more elements to the beginning of an array and returns the new length of the array:
var a = [1, 2, 3];
a.unshift(4, 5);
console.log(a);
Output:
[4, 5, 1, 2, 3]
3) The concat() method is used to merge two or more arrays. This method does not change the existing arrays, but instead returns a new array.
var arr1 = ["a", "b", "c"];
var arr2 = ["d", "e", "f"];
var arr3 = arr1.concat(arr2);
console.log(arr3);
Output:
[ "a", "b", "c", "d", "e", "f" ]
4) You can use the array's .length property to add an element to the end of the array:
var ar = ['one', 'two', 'three'];
ar[ar.length] = 'four';
console.log( ar );
Output:
["one", "two", "three", "four"]
5) The splice() method changes the content of an array by removing existing elements and/or adding new elements:
var myFish = ["angel", "clown", "mandarin", "surgeon"];
myFish.splice(4, 0, "nemo");
//array.splice(start, deleteCount, item1, item2, ...)
console.log(myFish);
Output:
["angel", "clown", "mandarin", "surgeon","nemo"]
6) You can also add a new element to an array simply by specifying a new index and assigning a value:
var ar = ['one', 'two', 'three'];
ar[3] = 'four'; // add new element to ar
console.log(ar);
Output:
["one", "two","three","four"]
The push() method adds new items to the end of an array, and returns the new length. Example:
var fruits = ["Banana", "Orange", "Apple", "Mango"];
fruits.push("Kiwi");
// The result of fruits will be:
Banana, Orange, Apple, Mango, Kiwi
The exact answer to your question is already answered, but let's look at some other ways to add items to an array.
The unshift() method adds new items to the beginning of an array, and returns the new length. Example:
var fruits = ["Banana", "Orange", "Apple", "Mango"];
fruits.unshift("Lemon", "Pineapple");
// The result of fruits will be:
Lemon, Pineapple, Banana, Orange, Apple, Mango
And lastly, the concat() method is used to join two or more arrays. Example:
var fruits = ["Banana", "Orange"];
var moreFruits = ["Apple", "Mango", "Lemon"];
var allFruits = fruits.concat(moreFruits);
// The values of the children array will be:
Banana, Orange, Apple, Mango, Lemon
Now, you can take advantage of ES6 syntax and just do
let array = [1, 2];
console.log([...array, 3]);
keeping the original array immutable.
Append a single element
// Append to the end
arrName.push('newName1');
// Prepend to the start
arrName.unshift('newName1');
// Insert at index 1
arrName.splice(1, 0,'newName1');
// 1: index number, 0: number of element to remove, newName1: new element
// Replace index 3 (of exists), add new element otherwise.
arrName[3] = 'newName1';
Append multiple elements
// Insert from index number 1
arrName.splice(1, 0,'newElemenet1', 'newElemenet2', 'newElemenet3');
// 1: index number from where insert starts,
// 0: number of element to remove,
//newElemenet1,2,3: new elements
Append an array
// Join two or more arrays
arrName.concat(newAry1, newAry2);
//newAry1,newAry2: Two different arrays which are to be combined (concatenated) to an existing array
If you know the highest index (such as stored in a variable "i") then you can do
myArray[i + 1] = someValue;
However, if you don't know then you can either use
myArray.push(someValue);
as other answers suggested, or you can use
myArray[myArray.length] = someValue;
Note that the array is zero based so .length returns the highest index plus one.
Also note that you don't have to add in order and you can actually skip values, as in
myArray[myArray.length + 1000] = someValue;
In which case the values in between will have a value of undefined.
It is therefore a good practice when looping through a JavaScript to verify that a value actually exists at that point.
This can be done by something like the following:
if(myArray[i] === "undefined"){ continue; }
If you are certain that you don't have any zeros in the array then you can just do:
if(!myArray[i]){ continue; }
Of course, make sure in this case that you don't use as the condition myArray[i] (as some people over the Internet suggest based on the end that as soon as i is greater than the highest index, it will return undefined which evaluates to false).
You can do it using JavaScript Spread Operator Syntax:
// Initialize the array
var arr = [
"Hi",
"Hello",
"Bangladesh"
];
// Append a new value to the array
arr = [...arr, "Feni"];
// Or you can add a variable value
var testValue = "Cool";
arr = [...arr, testValue ];
console.log(arr);
// Final output [ 'Hi', 'Hello', 'Bangladesh', 'Feni', 'Cool' ]
If you are using ES6 you can use spread operator to do it.
var arr = [
"apple",
"banana",
"cherry"
];
var arr2 = [
"dragonfruit",
"elderberry",
"fig"
];
arr.push(...arr2);
concat(), of course, can be used with two-dimensional arrays as well. No looping required.
var a = [
[1, 2],
[3, 4] ];
var b = [
["a", "b"],
["c", "d"] ];
b = b.concat(a);
alert(b[2][1]); // Result: 2
Just want to add a snippet for non-destructive addition of an element.
var newArr = oldArr.concat([newEl]);
Let the array length property do the work:
myarray[myarray.length] = 'new element value added to the end of the array';
myarray.length returns the number of strings in the array.
JavaScript is zero-based, so the next element key of the array will be the current length of the array.
Example:
var myarray = [0, 1, 2, 3],
myarrayLength = myarray.length; // myarrayLength is set to 4
Append a value to an array
Since Array.prototype.push adds one or more elements to the end of an array and returns the new length of the array, sometimes we want just to get the new up-to-date array so we can do something like so:
const arr = [1, 2, 3];
const val = 4;
arr.concat([val]); // [1, 2, 3, 4]
Or just:
[...arr, val] // [1, 2, 3, 4]
Append a single item
To append a single item to an array, use the push() method provided by the Array object:
const fruits = ['banana', 'pear', 'apple']
fruits.push('mango')
console.log(fruits)
push() mutates the original array.
To create a new array instead, use the concat() Array method:
const fruits = ['banana', 'pear', 'apple']
const allfruits = fruits.concat('mango')
console.log(allfruits)
Notice that concat() does not actually add an item to the array, but creates a new array, which you can assign to another variable, or reassign to the original array (declaring it as let, as you cannot reassign a const):
const fruits = ['banana', 'pear', 'apple']
const allfruits = fruits.concat('mango')
console.log(allfruits)
let fruits = ['banana', 'pear', 'apple']
fruits = fruits.concat('mango')
Append multiple items
To append a multiple item to an array, you can use push() by calling it with multiple arguments:
const fruits = ['banana', 'pear', 'apple']
fruits.push('mango', 'melon', 'avocado')
console.log(fruits)
You can also use the concat() method you saw before, passing a list of items separated by a comma:
const fruits = ['banana', 'pear', 'apple']
const allfruits = fruits.concat('mango', 'melon', 'avocado')
console.log(allfruits)
or an array:
const fruits = ['banana', 'pear', 'apple']
const allfruits = fruits.concat(['mango', 'melon', 'avocado'])
console.log(allfruits)
Remember that as described previously this method does not mutate the original array, but it returns a new array.
Originally posted at
If you want to combine two arrays without the duplicate you may try the code below:
array_merge = function (arr1, arr2) {
return arr1.concat(arr2.filter(function(item){
return arr1.indexOf(item) < 0;
}))
}
Usage:
array1 = ['1', '2', '3']
array2 = ['2', '3', '4', '5']
combined_array = array_merge(array1, array2)
Output:
[1,2,3,4,5]
You .push() that value in.
Example: array.push(value);
If you want to append a single value into an array, simply use the push method. It will add a new element at the end of the array.
But if you intend to add multiple elements then store the elements in a new array and concat the second array with the first array...either way you wish.
arr=['a','b','c'];
arr.push('d');
//now print the array in console.log and it will contain 'a','b','c','d' as elements.
console.log(array);
We don't have an append function for Array in JavaScript, but we have push and unshift. Imagine you have the array below:
var arr = [1, 2, 3, 4, 5];
And we like to append a value to this array. We can do arr.push(6), and it will add 6 to the end of the array:
arr.push(6); // Returns [1, 2, 3, 4, 5, 6];
Also we can use unshift, look at how we can apply this:
arr.unshift(0); // Returns [0, 1, 2, 3, 4, 5];
They are main functions to add or append new values to the arrays.
You can use the push() if you want to add values,
e.g. arr.push("Test1", "Test2");.
If you have array you can use concat(), e.g. Array1.concat(Array2).
If you have just one element to add, you can also try the length method, e.g. array[aray.length] = 'test';.
Appending items on an array
let fruits = ["orange", "banana", "apple", "lemon"]; /* Array declaration */
fruits.push("avacado"); /* Adding an element to the array */
/* Displaying elements of the array */
for(var i=0; i < fruits.length; i++){
console.log(fruits[i]);
}
You can use the push method.
Array.prototype.append = function(destArray){
destArray = destArray || [];
this.push.call(this, ...destArray);
return this;
}
var arr = [1,2,5,67];
var arr1 = [7,4,7,8];
console.log(arr.append(arr1)); // [7, 4, 7, 8, 1, 4, 5, 67, 7]
console.log(arr.append("Hola")) // [1, 2, 5, 67, 7, 4, 7, 8, "H", "o", "l", "a"]
push() adds a new element to the end of an array.
pop() removes an element from the end of an array.
To append an object (such as a string or number) to an array, use:
array.push(toAppend);
This question's answers are a community effort. Edit existing answers to improve this post. It is not currently accepting new answers or interactions.
How do I append an object (such as a string or number) to an array in JavaScript?
Use the Array.prototype.push method to append values to the end of an array:
// initialize array
var arr = [
"Hi",
"Hello",
"Bonjour"
];
// append new value to the array
arr.push("Hola");
console.log(arr);
You can use the push() function to append more than one value to an array in a single call:
// initialize array
var arr = ["Hi", "Hello", "Bonjour", "Hola"];
// append multiple values to the array
arr.push("Salut", "Hey");
// display all values
for (var i = 0; i < arr.length; i++) {
console.log(arr[i]);
}
Update
If you want to add the items of one array to another array, you can use firstArray.concat(secondArray):
var arr = [
"apple",
"banana",
"cherry"
];
// Do not forget to assign the result as, unlike push, concat does not change the existing array
arr = arr.concat([
"dragonfruit",
"elderberry",
"fig"
]);
console.log(arr);
Update
Just an addition to this answer if you want to prepend any value to the start of an array (i.e. first index) then you can use Array.prototype.unshift for this purpose.
var arr = [1, 2, 3];
arr.unshift(0);
console.log(arr);
It also supports appending multiple values at once just like push.
Update
Another way with ES6 syntax is to return a new array with the spread syntax. This leaves the original array unchanged, but returns a new array with new items appended, compliant with the spirit of functional programming.
const arr = [
"Hi",
"Hello",
"Bonjour",
];
const newArr = [
...arr,
"Salut",
];
console.log(newArr);
If you're only appending a single variable, then push() works just fine. If you need to append another array, use concat():
var ar1 = [1, 2, 3];
var ar2 = [4, 5, 6];
var ar3 = ar1.concat(ar2);
alert(ar1);
alert(ar2);
alert(ar3);
The concat does not affect ar1 and ar2 unless reassigned, for example:
var ar1 = [1, 2, 3];
var ar2 = [4, 5, 6];
ar1 = ar1.concat(ar2);
alert(ar1);
There is a lot of great information on JavaScript Reference.
Some quick benchmarking (each test = 500k appended elements and the results are averages of multiple runs) showed the following:
Firefox 3.6 (Mac):
Small arrays: arr[arr.length] = b is faster (300ms vs. 800ms)
Large arrays: arr.push(b) is faster (500ms vs. 900ms)
Safari 5.0 (Mac):
Small arrays: arr[arr.length] = b is faster (90ms vs. 115ms)
Large arrays: arr[arr.length] = b is faster (160ms vs. 185ms)
Google Chrome 6.0 (Mac):
Small arrays: No significant difference (and Chrome is FAST! Only ~38ms !!)
Large arrays: No significant difference (160ms)
I like the arr.push() syntax better, but I think I'd be better off with the arr[arr.length] Version, at least in raw speed. I'd love to see the results of an IE run though.
My benchmarking loops:
function arrpush_small() {
var arr1 = [];
for (a = 0; a < 100; a++)
{
arr1 = [];
for (i = 0; i < 5000; i++)
{
arr1.push('elem' + i);
}
}
}
function arrlen_small() {
var arr2 = [];
for (b = 0; b < 100; b++)
{
arr2 = [];
for (j = 0; j < 5000; j++)
{
arr2[arr2.length] = 'elem' + j;
}
}
}
function arrpush_large() {
var arr1 = [];
for (i = 0; i < 500000; i++)
{
arr1.push('elem' + i);
}
}
function arrlen_large() {
var arr2 = [];
for (j = 0; j < 500000; j++)
{
arr2[arr2.length] = 'elem' + j;
}
}
I think it's worth mentioning that push can be called with multiple arguments, which will be appended to the array in order. For example:
var arr = ['first'];
arr.push('second', 'third');
console.log(arr);
As a result of this you can use push.apply to append an array to another array like so:
var arr = ['first'];
arr.push('second', 'third');
arr.push.apply(arr, ['forth', 'fifth']);
console.log(arr);
Annotated ES5 has more info on exactly what push and apply do.
2016 update: with spread, you don't need that apply anymore, like:
var arr = ['first'];
arr.push('second', 'third');
arr.push(...['fourth', 'fifth']);
console.log(arr) ;
You can use the push and apply functions to append two arrays.
var array1 = [11, 32, 75];
var array2 = [99, 67, 34];
Array.prototype.push.apply(array1, array2);
console.log(array1);
It will append array2 to array1. Now array1 contains [11, 32, 75, 99, 67, 34].
This code is much simpler than writing for loops to copy each and every items in the array.
With the new ES6 spread operator, joining two arrays using push becomes even easier:
var arr = [1, 2, 3, 4, 5];
var arr2 = [6, 7, 8, 9, 10];
arr.push(...arr2);
console.log(arr);
This adds the contents of arr2 onto the end of arr.
Babel REPL Example
If arr is an array, and val is the value you wish to add use:
arr.push(val);
E.g.
var arr = ['a', 'b', 'c'];
arr.push('d');
console.log(arr);
Use concat:
a = [1, 2, 3];
b = [3, 4, 5];
a = a.concat(b);
console.log(a);
JavaScript with the ECMAScript 5 (ES5) standard which is supported by most browsers now, you can use apply() to append array1 to array2.
var array1 = [3, 4, 5];
var array2 = [1, 2];
Array.prototype.push.apply(array2, array1);
console.log(array2); // [1, 2, 3, 4, 5]
JavaScript with ECMAScript 6 (ES6) standard which is supported by Chrome, Firefox, Internet Explorer, and Edge, you can use the spread operator:
"use strict";
let array1 = [3, 4, 5];
let array2 = [1, 2];
array2.push(...array1);
console.log(array2); // [1, 2, 3, 4, 5]
The spread operator will replace array2.push(...array1); with array2.push(3, 4, 5); when the browser is thinking the logic.
Bonus point
If you'd like to create another variable to store all the items from both arrays, you can do this:
ES5 var combinedArray = array1.concat(array2);
ES6 const combinedArray = [...array1, ...array2]
The spread operator (...) is to spread out all items from a collection.
If you want to append two arrays -
var a = ['a', 'b'];
var b = ['c', 'd'];
then you could use:
var c = a.concat(b);
And if you want to add record g to array (var a=[]) then you could use:
a.push('g');
There are a couple of ways to append an array in JavaScript:
1) The push() method adds one or more elements to the end of an array and returns the new length of the array.
var a = [1, 2, 3];
a.push(4, 5);
console.log(a);
Output:
[1, 2, 3, 4, 5]
2) The unshift() method adds one or more elements to the beginning of an array and returns the new length of the array:
var a = [1, 2, 3];
a.unshift(4, 5);
console.log(a);
Output:
[4, 5, 1, 2, 3]
3) The concat() method is used to merge two or more arrays. This method does not change the existing arrays, but instead returns a new array.
var arr1 = ["a", "b", "c"];
var arr2 = ["d", "e", "f"];
var arr3 = arr1.concat(arr2);
console.log(arr3);
Output:
[ "a", "b", "c", "d", "e", "f" ]
4) You can use the array's .length property to add an element to the end of the array:
var ar = ['one', 'two', 'three'];
ar[ar.length] = 'four';
console.log( ar );
Output:
["one", "two", "three", "four"]
5) The splice() method changes the content of an array by removing existing elements and/or adding new elements:
var myFish = ["angel", "clown", "mandarin", "surgeon"];
myFish.splice(4, 0, "nemo");
//array.splice(start, deleteCount, item1, item2, ...)
console.log(myFish);
Output:
["angel", "clown", "mandarin", "surgeon","nemo"]
6) You can also add a new element to an array simply by specifying a new index and assigning a value:
var ar = ['one', 'two', 'three'];
ar[3] = 'four'; // add new element to ar
console.log(ar);
Output:
["one", "two","three","four"]
The push() method adds new items to the end of an array, and returns the new length. Example:
var fruits = ["Banana", "Orange", "Apple", "Mango"];
fruits.push("Kiwi");
// The result of fruits will be:
Banana, Orange, Apple, Mango, Kiwi
The exact answer to your question is already answered, but let's look at some other ways to add items to an array.
The unshift() method adds new items to the beginning of an array, and returns the new length. Example:
var fruits = ["Banana", "Orange", "Apple", "Mango"];
fruits.unshift("Lemon", "Pineapple");
// The result of fruits will be:
Lemon, Pineapple, Banana, Orange, Apple, Mango
And lastly, the concat() method is used to join two or more arrays. Example:
var fruits = ["Banana", "Orange"];
var moreFruits = ["Apple", "Mango", "Lemon"];
var allFruits = fruits.concat(moreFruits);
// The values of the children array will be:
Banana, Orange, Apple, Mango, Lemon
Now, you can take advantage of ES6 syntax and just do
let array = [1, 2];
console.log([...array, 3]);
keeping the original array immutable.
Append a single element
// Append to the end
arrName.push('newName1');
// Prepend to the start
arrName.unshift('newName1');
// Insert at index 1
arrName.splice(1, 0,'newName1');
// 1: index number, 0: number of element to remove, newName1: new element
// Replace index 3 (of exists), add new element otherwise.
arrName[3] = 'newName1';
Append multiple elements
// Insert from index number 1
arrName.splice(1, 0,'newElemenet1', 'newElemenet2', 'newElemenet3');
// 1: index number from where insert starts,
// 0: number of element to remove,
//newElemenet1,2,3: new elements
Append an array
// Join two or more arrays
arrName.concat(newAry1, newAry2);
//newAry1,newAry2: Two different arrays which are to be combined (concatenated) to an existing array
If you know the highest index (such as stored in a variable "i") then you can do
myArray[i + 1] = someValue;
However, if you don't know then you can either use
myArray.push(someValue);
as other answers suggested, or you can use
myArray[myArray.length] = someValue;
Note that the array is zero based so .length returns the highest index plus one.
Also note that you don't have to add in order and you can actually skip values, as in
myArray[myArray.length + 1000] = someValue;
In which case the values in between will have a value of undefined.
It is therefore a good practice when looping through a JavaScript to verify that a value actually exists at that point.
This can be done by something like the following:
if(myArray[i] === "undefined"){ continue; }
If you are certain that you don't have any zeros in the array then you can just do:
if(!myArray[i]){ continue; }
Of course, make sure in this case that you don't use as the condition myArray[i] (as some people over the Internet suggest based on the end that as soon as i is greater than the highest index, it will return undefined which evaluates to false).
You can do it using JavaScript Spread Operator Syntax:
// Initialize the array
var arr = [
"Hi",
"Hello",
"Bangladesh"
];
// Append a new value to the array
arr = [...arr, "Feni"];
// Or you can add a variable value
var testValue = "Cool";
arr = [...arr, testValue ];
console.log(arr);
// Final output [ 'Hi', 'Hello', 'Bangladesh', 'Feni', 'Cool' ]
If you are using ES6 you can use spread operator to do it.
var arr = [
"apple",
"banana",
"cherry"
];
var arr2 = [
"dragonfruit",
"elderberry",
"fig"
];
arr.push(...arr2);
concat(), of course, can be used with two-dimensional arrays as well. No looping required.
var a = [
[1, 2],
[3, 4] ];
var b = [
["a", "b"],
["c", "d"] ];
b = b.concat(a);
alert(b[2][1]); // Result: 2
Just want to add a snippet for non-destructive addition of an element.
var newArr = oldArr.concat([newEl]);
Let the array length property do the work:
myarray[myarray.length] = 'new element value added to the end of the array';
myarray.length returns the number of strings in the array.
JavaScript is zero-based, so the next element key of the array will be the current length of the array.
Example:
var myarray = [0, 1, 2, 3],
myarrayLength = myarray.length; // myarrayLength is set to 4
Append a value to an array
Since Array.prototype.push adds one or more elements to the end of an array and returns the new length of the array, sometimes we want just to get the new up-to-date array so we can do something like so:
const arr = [1, 2, 3];
const val = 4;
arr.concat([val]); // [1, 2, 3, 4]
Or just:
[...arr, val] // [1, 2, 3, 4]
Append a single item
To append a single item to an array, use the push() method provided by the Array object:
const fruits = ['banana', 'pear', 'apple']
fruits.push('mango')
console.log(fruits)
push() mutates the original array.
To create a new array instead, use the concat() Array method:
const fruits = ['banana', 'pear', 'apple']
const allfruits = fruits.concat('mango')
console.log(allfruits)
Notice that concat() does not actually add an item to the array, but creates a new array, which you can assign to another variable, or reassign to the original array (declaring it as let, as you cannot reassign a const):
const fruits = ['banana', 'pear', 'apple']
const allfruits = fruits.concat('mango')
console.log(allfruits)
let fruits = ['banana', 'pear', 'apple']
fruits = fruits.concat('mango')
Append multiple items
To append a multiple item to an array, you can use push() by calling it with multiple arguments:
const fruits = ['banana', 'pear', 'apple']
fruits.push('mango', 'melon', 'avocado')
console.log(fruits)
You can also use the concat() method you saw before, passing a list of items separated by a comma:
const fruits = ['banana', 'pear', 'apple']
const allfruits = fruits.concat('mango', 'melon', 'avocado')
console.log(allfruits)
or an array:
const fruits = ['banana', 'pear', 'apple']
const allfruits = fruits.concat(['mango', 'melon', 'avocado'])
console.log(allfruits)
Remember that as described previously this method does not mutate the original array, but it returns a new array.
Originally posted at
If you want to combine two arrays without the duplicate you may try the code below:
array_merge = function (arr1, arr2) {
return arr1.concat(arr2.filter(function(item){
return arr1.indexOf(item) < 0;
}))
}
Usage:
array1 = ['1', '2', '3']
array2 = ['2', '3', '4', '5']
combined_array = array_merge(array1, array2)
Output:
[1,2,3,4,5]
You .push() that value in.
Example: array.push(value);
If you want to append a single value into an array, simply use the push method. It will add a new element at the end of the array.
But if you intend to add multiple elements then store the elements in a new array and concat the second array with the first array...either way you wish.
arr=['a','b','c'];
arr.push('d');
//now print the array in console.log and it will contain 'a','b','c','d' as elements.
console.log(array);
We don't have an append function for Array in JavaScript, but we have push and unshift. Imagine you have the array below:
var arr = [1, 2, 3, 4, 5];
And we like to append a value to this array. We can do arr.push(6), and it will add 6 to the end of the array:
arr.push(6); // Returns [1, 2, 3, 4, 5, 6];
Also we can use unshift, look at how we can apply this:
arr.unshift(0); // Returns [0, 1, 2, 3, 4, 5];
They are main functions to add or append new values to the arrays.
You can use the push() if you want to add values,
e.g. arr.push("Test1", "Test2");.
If you have array you can use concat(), e.g. Array1.concat(Array2).
If you have just one element to add, you can also try the length method, e.g. array[aray.length] = 'test';.
Appending items on an array
let fruits = ["orange", "banana", "apple", "lemon"]; /* Array declaration */
fruits.push("avacado"); /* Adding an element to the array */
/* Displaying elements of the array */
for(var i=0; i < fruits.length; i++){
console.log(fruits[i]);
}
You can use the push method.
Array.prototype.append = function(destArray){
destArray = destArray || [];
this.push.call(this, ...destArray);
return this;
}
var arr = [1,2,5,67];
var arr1 = [7,4,7,8];
console.log(arr.append(arr1)); // [7, 4, 7, 8, 1, 4, 5, 67, 7]
console.log(arr.append("Hola")) // [1, 2, 5, 67, 7, 4, 7, 8, "H", "o", "l", "a"]
push() adds a new element to the end of an array.
pop() removes an element from the end of an array.
To append an object (such as a string or number) to an array, use:
array.push(toAppend);
For example i have a array like that
var myArray = [
[1,2,3],
[4,5,6],
[7,8,9,10],
[[11,12],[13,14,15]]];
for (var i = 0;i < myArray.length;i++){
for(var j = 0 ;j< myArray[i].length;j++){
for(var k = 0;k< myArray[i][j].length;k++){
console.log(myArray[i],[j][k]);
}
}
}
But output is only 11,12,13,14,15.
And i wanna print all the values
Could some one help to fix
Thank you in advance
Use e.g. Array.prototype.flat(), .flat(2) flattens to the level of 2 arrays deep.
var myArray = [
[1,2,3],
[4,5,6],
[7,8,9,10],
[[11,12],[13,14,15]]];
console.log(myArray.flat(2));
You can use recursive function
first pass it the whole array then loop it and check if the element you are accessing is array or digit
if its array call the same function again and only pass it this element
otherwise if its digit just print it
This works even when you dont know how many nested arrays you have otherwise use MWO answer
var myArray = [
[1,2,3],
[4,5,6],
[7,8,9,10],
[[11,12],[13,14,15]]];
function printArray(arr){
for(var i = 0; i < arr.length; i++){
if(Array.isArray(arr[i])){
printArray(arr[i]);
}else{
console.log(arr[i]);
}
}
}
printArray(myArray);
This fucntion works for any depth of multi dimensional array. Using Recursion
var myArray = [1,2,33,44, [1,2,3], [[11,12],[13,14,15]]];
var myArray1 = [1,2,33,44, [[11,12],[13,14,15]]];
var deepFlattenArray = function (array){
var result = [];
array.forEach(function (element) {
if (Array.isArray(element)) {
result = result.concat(deepFlattenArray(element));
} else {
result.push(element);
}
});
return result;
};
console.log(deepFlattenArray(myArray));
// output = [ 1, 2, 33, 44, 1, 2, 3, 11, 12, 13, 14, 15]
console.log(deepFlattenArray(myArray1));
// output = [1, 2, 33, 44, 11, 12, 13, 14, 15 ]
This question's answers are a community effort. Edit existing answers to improve this post. It is not currently accepting new answers or interactions.
How do I append an object (such as a string or number) to an array in JavaScript?
Use the Array.prototype.push method to append values to the end of an array:
// initialize array
var arr = [
"Hi",
"Hello",
"Bonjour"
];
// append new value to the array
arr.push("Hola");
console.log(arr);
You can use the push() function to append more than one value to an array in a single call:
// initialize array
var arr = ["Hi", "Hello", "Bonjour", "Hola"];
// append multiple values to the array
arr.push("Salut", "Hey");
// display all values
for (var i = 0; i < arr.length; i++) {
console.log(arr[i]);
}
Update
If you want to add the items of one array to another array, you can use firstArray.concat(secondArray):
var arr = [
"apple",
"banana",
"cherry"
];
// Do not forget to assign the result as, unlike push, concat does not change the existing array
arr = arr.concat([
"dragonfruit",
"elderberry",
"fig"
]);
console.log(arr);
Update
Just an addition to this answer if you want to prepend any value to the start of an array (i.e. first index) then you can use Array.prototype.unshift for this purpose.
var arr = [1, 2, 3];
arr.unshift(0);
console.log(arr);
It also supports appending multiple values at once just like push.
Update
Another way with ES6 syntax is to return a new array with the spread syntax. This leaves the original array unchanged, but returns a new array with new items appended, compliant with the spirit of functional programming.
const arr = [
"Hi",
"Hello",
"Bonjour",
];
const newArr = [
...arr,
"Salut",
];
console.log(newArr);
If you're only appending a single variable, then push() works just fine. If you need to append another array, use concat():
var ar1 = [1, 2, 3];
var ar2 = [4, 5, 6];
var ar3 = ar1.concat(ar2);
alert(ar1);
alert(ar2);
alert(ar3);
The concat does not affect ar1 and ar2 unless reassigned, for example:
var ar1 = [1, 2, 3];
var ar2 = [4, 5, 6];
ar1 = ar1.concat(ar2);
alert(ar1);
There is a lot of great information on JavaScript Reference.
Some quick benchmarking (each test = 500k appended elements and the results are averages of multiple runs) showed the following:
Firefox 3.6 (Mac):
Small arrays: arr[arr.length] = b is faster (300ms vs. 800ms)
Large arrays: arr.push(b) is faster (500ms vs. 900ms)
Safari 5.0 (Mac):
Small arrays: arr[arr.length] = b is faster (90ms vs. 115ms)
Large arrays: arr[arr.length] = b is faster (160ms vs. 185ms)
Google Chrome 6.0 (Mac):
Small arrays: No significant difference (and Chrome is FAST! Only ~38ms !!)
Large arrays: No significant difference (160ms)
I like the arr.push() syntax better, but I think I'd be better off with the arr[arr.length] Version, at least in raw speed. I'd love to see the results of an IE run though.
My benchmarking loops:
function arrpush_small() {
var arr1 = [];
for (a = 0; a < 100; a++)
{
arr1 = [];
for (i = 0; i < 5000; i++)
{
arr1.push('elem' + i);
}
}
}
function arrlen_small() {
var arr2 = [];
for (b = 0; b < 100; b++)
{
arr2 = [];
for (j = 0; j < 5000; j++)
{
arr2[arr2.length] = 'elem' + j;
}
}
}
function arrpush_large() {
var arr1 = [];
for (i = 0; i < 500000; i++)
{
arr1.push('elem' + i);
}
}
function arrlen_large() {
var arr2 = [];
for (j = 0; j < 500000; j++)
{
arr2[arr2.length] = 'elem' + j;
}
}
I think it's worth mentioning that push can be called with multiple arguments, which will be appended to the array in order. For example:
var arr = ['first'];
arr.push('second', 'third');
console.log(arr);
As a result of this you can use push.apply to append an array to another array like so:
var arr = ['first'];
arr.push('second', 'third');
arr.push.apply(arr, ['forth', 'fifth']);
console.log(arr);
Annotated ES5 has more info on exactly what push and apply do.
2016 update: with spread, you don't need that apply anymore, like:
var arr = ['first'];
arr.push('second', 'third');
arr.push(...['fourth', 'fifth']);
console.log(arr) ;
You can use the push and apply functions to append two arrays.
var array1 = [11, 32, 75];
var array2 = [99, 67, 34];
Array.prototype.push.apply(array1, array2);
console.log(array1);
It will append array2 to array1. Now array1 contains [11, 32, 75, 99, 67, 34].
This code is much simpler than writing for loops to copy each and every items in the array.
With the new ES6 spread operator, joining two arrays using push becomes even easier:
var arr = [1, 2, 3, 4, 5];
var arr2 = [6, 7, 8, 9, 10];
arr.push(...arr2);
console.log(arr);
This adds the contents of arr2 onto the end of arr.
Babel REPL Example
If arr is an array, and val is the value you wish to add use:
arr.push(val);
E.g.
var arr = ['a', 'b', 'c'];
arr.push('d');
console.log(arr);
Use concat:
a = [1, 2, 3];
b = [3, 4, 5];
a = a.concat(b);
console.log(a);
JavaScript with the ECMAScript 5 (ES5) standard which is supported by most browsers now, you can use apply() to append array1 to array2.
var array1 = [3, 4, 5];
var array2 = [1, 2];
Array.prototype.push.apply(array2, array1);
console.log(array2); // [1, 2, 3, 4, 5]
JavaScript with ECMAScript 6 (ES6) standard which is supported by Chrome, Firefox, Internet Explorer, and Edge, you can use the spread operator:
"use strict";
let array1 = [3, 4, 5];
let array2 = [1, 2];
array2.push(...array1);
console.log(array2); // [1, 2, 3, 4, 5]
The spread operator will replace array2.push(...array1); with array2.push(3, 4, 5); when the browser is thinking the logic.
Bonus point
If you'd like to create another variable to store all the items from both arrays, you can do this:
ES5 var combinedArray = array1.concat(array2);
ES6 const combinedArray = [...array1, ...array2]
The spread operator (...) is to spread out all items from a collection.
If you want to append two arrays -
var a = ['a', 'b'];
var b = ['c', 'd'];
then you could use:
var c = a.concat(b);
And if you want to add record g to array (var a=[]) then you could use:
a.push('g');
There are a couple of ways to append an array in JavaScript:
1) The push() method adds one or more elements to the end of an array and returns the new length of the array.
var a = [1, 2, 3];
a.push(4, 5);
console.log(a);
Output:
[1, 2, 3, 4, 5]
2) The unshift() method adds one or more elements to the beginning of an array and returns the new length of the array:
var a = [1, 2, 3];
a.unshift(4, 5);
console.log(a);
Output:
[4, 5, 1, 2, 3]
3) The concat() method is used to merge two or more arrays. This method does not change the existing arrays, but instead returns a new array.
var arr1 = ["a", "b", "c"];
var arr2 = ["d", "e", "f"];
var arr3 = arr1.concat(arr2);
console.log(arr3);
Output:
[ "a", "b", "c", "d", "e", "f" ]
4) You can use the array's .length property to add an element to the end of the array:
var ar = ['one', 'two', 'three'];
ar[ar.length] = 'four';
console.log( ar );
Output:
["one", "two", "three", "four"]
5) The splice() method changes the content of an array by removing existing elements and/or adding new elements:
var myFish = ["angel", "clown", "mandarin", "surgeon"];
myFish.splice(4, 0, "nemo");
//array.splice(start, deleteCount, item1, item2, ...)
console.log(myFish);
Output:
["angel", "clown", "mandarin", "surgeon","nemo"]
6) You can also add a new element to an array simply by specifying a new index and assigning a value:
var ar = ['one', 'two', 'three'];
ar[3] = 'four'; // add new element to ar
console.log(ar);
Output:
["one", "two","three","four"]
The push() method adds new items to the end of an array, and returns the new length. Example:
var fruits = ["Banana", "Orange", "Apple", "Mango"];
fruits.push("Kiwi");
// The result of fruits will be:
Banana, Orange, Apple, Mango, Kiwi
The exact answer to your question is already answered, but let's look at some other ways to add items to an array.
The unshift() method adds new items to the beginning of an array, and returns the new length. Example:
var fruits = ["Banana", "Orange", "Apple", "Mango"];
fruits.unshift("Lemon", "Pineapple");
// The result of fruits will be:
Lemon, Pineapple, Banana, Orange, Apple, Mango
And lastly, the concat() method is used to join two or more arrays. Example:
var fruits = ["Banana", "Orange"];
var moreFruits = ["Apple", "Mango", "Lemon"];
var allFruits = fruits.concat(moreFruits);
// The values of the children array will be:
Banana, Orange, Apple, Mango, Lemon
Now, you can take advantage of ES6 syntax and just do
let array = [1, 2];
console.log([...array, 3]);
keeping the original array immutable.
Append a single element
// Append to the end
arrName.push('newName1');
// Prepend to the start
arrName.unshift('newName1');
// Insert at index 1
arrName.splice(1, 0,'newName1');
// 1: index number, 0: number of element to remove, newName1: new element
// Replace index 3 (of exists), add new element otherwise.
arrName[3] = 'newName1';
Append multiple elements
// Insert from index number 1
arrName.splice(1, 0,'newElemenet1', 'newElemenet2', 'newElemenet3');
// 1: index number from where insert starts,
// 0: number of element to remove,
//newElemenet1,2,3: new elements
Append an array
// Join two or more arrays
arrName.concat(newAry1, newAry2);
//newAry1,newAry2: Two different arrays which are to be combined (concatenated) to an existing array
If you know the highest index (such as stored in a variable "i") then you can do
myArray[i + 1] = someValue;
However, if you don't know then you can either use
myArray.push(someValue);
as other answers suggested, or you can use
myArray[myArray.length] = someValue;
Note that the array is zero based so .length returns the highest index plus one.
Also note that you don't have to add in order and you can actually skip values, as in
myArray[myArray.length + 1000] = someValue;
In which case the values in between will have a value of undefined.
It is therefore a good practice when looping through a JavaScript to verify that a value actually exists at that point.
This can be done by something like the following:
if(myArray[i] === "undefined"){ continue; }
If you are certain that you don't have any zeros in the array then you can just do:
if(!myArray[i]){ continue; }
Of course, make sure in this case that you don't use as the condition myArray[i] (as some people over the Internet suggest based on the end that as soon as i is greater than the highest index, it will return undefined which evaluates to false).
You can do it using JavaScript Spread Operator Syntax:
// Initialize the array
var arr = [
"Hi",
"Hello",
"Bangladesh"
];
// Append a new value to the array
arr = [...arr, "Feni"];
// Or you can add a variable value
var testValue = "Cool";
arr = [...arr, testValue ];
console.log(arr);
// Final output [ 'Hi', 'Hello', 'Bangladesh', 'Feni', 'Cool' ]
If you are using ES6 you can use spread operator to do it.
var arr = [
"apple",
"banana",
"cherry"
];
var arr2 = [
"dragonfruit",
"elderberry",
"fig"
];
arr.push(...arr2);
concat(), of course, can be used with two-dimensional arrays as well. No looping required.
var a = [
[1, 2],
[3, 4] ];
var b = [
["a", "b"],
["c", "d"] ];
b = b.concat(a);
alert(b[2][1]); // Result: 2
Just want to add a snippet for non-destructive addition of an element.
var newArr = oldArr.concat([newEl]);
Let the array length property do the work:
myarray[myarray.length] = 'new element value added to the end of the array';
myarray.length returns the number of strings in the array.
JavaScript is zero-based, so the next element key of the array will be the current length of the array.
Example:
var myarray = [0, 1, 2, 3],
myarrayLength = myarray.length; // myarrayLength is set to 4
Append a value to an array
Since Array.prototype.push adds one or more elements to the end of an array and returns the new length of the array, sometimes we want just to get the new up-to-date array so we can do something like so:
const arr = [1, 2, 3];
const val = 4;
arr.concat([val]); // [1, 2, 3, 4]
Or just:
[...arr, val] // [1, 2, 3, 4]
Append a single item
To append a single item to an array, use the push() method provided by the Array object:
const fruits = ['banana', 'pear', 'apple']
fruits.push('mango')
console.log(fruits)
push() mutates the original array.
To create a new array instead, use the concat() Array method:
const fruits = ['banana', 'pear', 'apple']
const allfruits = fruits.concat('mango')
console.log(allfruits)
Notice that concat() does not actually add an item to the array, but creates a new array, which you can assign to another variable, or reassign to the original array (declaring it as let, as you cannot reassign a const):
const fruits = ['banana', 'pear', 'apple']
const allfruits = fruits.concat('mango')
console.log(allfruits)
let fruits = ['banana', 'pear', 'apple']
fruits = fruits.concat('mango')
Append multiple items
To append a multiple item to an array, you can use push() by calling it with multiple arguments:
const fruits = ['banana', 'pear', 'apple']
fruits.push('mango', 'melon', 'avocado')
console.log(fruits)
You can also use the concat() method you saw before, passing a list of items separated by a comma:
const fruits = ['banana', 'pear', 'apple']
const allfruits = fruits.concat('mango', 'melon', 'avocado')
console.log(allfruits)
or an array:
const fruits = ['banana', 'pear', 'apple']
const allfruits = fruits.concat(['mango', 'melon', 'avocado'])
console.log(allfruits)
Remember that as described previously this method does not mutate the original array, but it returns a new array.
Originally posted at
If you want to combine two arrays without the duplicate you may try the code below:
array_merge = function (arr1, arr2) {
return arr1.concat(arr2.filter(function(item){
return arr1.indexOf(item) < 0;
}))
}
Usage:
array1 = ['1', '2', '3']
array2 = ['2', '3', '4', '5']
combined_array = array_merge(array1, array2)
Output:
[1,2,3,4,5]
You .push() that value in.
Example: array.push(value);
If you want to append a single value into an array, simply use the push method. It will add a new element at the end of the array.
But if you intend to add multiple elements then store the elements in a new array and concat the second array with the first array...either way you wish.
arr=['a','b','c'];
arr.push('d');
//now print the array in console.log and it will contain 'a','b','c','d' as elements.
console.log(array);
We don't have an append function for Array in JavaScript, but we have push and unshift. Imagine you have the array below:
var arr = [1, 2, 3, 4, 5];
And we like to append a value to this array. We can do arr.push(6), and it will add 6 to the end of the array:
arr.push(6); // Returns [1, 2, 3, 4, 5, 6];
Also we can use unshift, look at how we can apply this:
arr.unshift(0); // Returns [0, 1, 2, 3, 4, 5];
They are main functions to add or append new values to the arrays.
You can use the push() if you want to add values,
e.g. arr.push("Test1", "Test2");.
If you have array you can use concat(), e.g. Array1.concat(Array2).
If you have just one element to add, you can also try the length method, e.g. array[aray.length] = 'test';.
Appending items on an array
let fruits = ["orange", "banana", "apple", "lemon"]; /* Array declaration */
fruits.push("avacado"); /* Adding an element to the array */
/* Displaying elements of the array */
for(var i=0; i < fruits.length; i++){
console.log(fruits[i]);
}
You can use the push method.
Array.prototype.append = function(destArray){
destArray = destArray || [];
this.push.call(this, ...destArray);
return this;
}
var arr = [1,2,5,67];
var arr1 = [7,4,7,8];
console.log(arr.append(arr1)); // [7, 4, 7, 8, 1, 4, 5, 67, 7]
console.log(arr.append("Hola")) // [1, 2, 5, 67, 7, 4, 7, 8, "H", "o", "l", "a"]
push() adds a new element to the end of an array.
pop() removes an element from the end of an array.
To append an object (such as a string or number) to an array, use:
array.push(toAppend);