How to push data to array with position [i]? - javascript

For example i've created an array in a for loop:
for (i = 0; i < data.length; i++){
array[i] = {
label: bread,
color: colorArray[i]
};
}
In a child for loop i'd like to append more data to this array. What I tried:
for (r = 0; r < data[i].length; r++){
array[i].push({
data: breadTypes[r][i]
});
}
Which throws TypeError : array[i].push is not a function.
array[r] = { data: breadTypes[r][i] }; overwrites the existing data as expected.
Is there a different way to do this? Thanks!

Here array[i] is an object and push is an array method which cannot be used on an object but you can create data key in array[i] object
array[r].data = breadTypes[r];
If the second loop is not nested inside the first one then breadTypes[r][i] will throw an error since i will be be available

Just do like this:
for (i = 0; i < data.length; ++i) {
array[i].data = breadTypes[i];
}

If i understand correctly, your second for should look like this:
for (r = 0; r < data[i].length; r++){
array[i].data = breadTypes[r][i];
}

Related

Js Math.random not random [duplicate]

I tried to get this to work, but the outer loop stops after second iteration, and everything that's after it does not execute(just like it was the end of the script). I want to fill two dimensional array with any character(here i used 'q' as an example)
var A=[[],[]];
for(var i=0;i<12;i++){
for(var j=0;j<81;j++){
A[i][j]='q';
}
}
It didn't work, so i put alert(i+' '+j); to see if it's even executing, and, as i wrote before, it stops after second iteration of outer loop, and then ignores rest of the script.
All I want is to have this array filled with same character in the given range(12 rows, 81 columns in this specific case), so if there's no hope in this method, i'll be glad to see one that works.
This does the job in one line.
var A = Array(12).fill(null).map(()=>Array(81).fill('q'))
This is an array of references and a bad idea as harunurhan commented.
var A = Array(12).fill(Array(81).fill('q'));
The Array.from() method creates a new, shallow-copied Array instance
from an array-like or iterable object.
function createAndFillTwoDArray({
rows,
columns,
defaultValue
}){
return Array.from({ length:rows }, () => (
Array.from({ length:columns }, ()=> defaultValue)
))
}
console.log(createAndFillTwoDArray({rows:3, columns:9, defaultValue: 'q'}))
var A=[[], []];
^ This line declares a two dimensional array of size 1x2. Try this instead:
var A = [];
for (var i = 0; i < 12; i++) {
A[i] = [];
for (var j = 0; j < 81; j++) {
A[i][j] = 'q';
}
}
Since fill() is the most succinct and intuitive, and it works as intended for immutable values, my preference would be an outer from() and an inner fill():
Array.from({length: 12}, _ => new Array(81).fill('q'));
The best approach to fill up 2D array would be like the following
let array2D = [], row = 3, col = 3, fillValue = 1
for (let i = 0; i < row; i++){
let temp = []
for (let j = 0; j < col; j++){
temp[j] = fillValue
}
array2D.push(temp)
}
You need to initialise a new array for i each time the first loop runs, and you don't need to set the layout of the array before you create it (Remove the [], [] inside the declaration of A). Try this:
var A = [];
for (var i = 0; i < 12; i++) {
A[i] = [];
for (var j = 0; j < 81; j++) {
A[i][j] = 'q';
}
}
console.log(A);
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max-height: 100% !important;
top: 0;
}

Grabbing String From Nested Array Using Nested Loops

I am a totally new to coding and I'm practicing loops and arrays. I created an array with multiple sub arrays that contain pairs of strings. I'm trying to pull out and isolate each string using a nested for loops.
Here is my code:
const pairs = [['Blue', 'Green'],['Red', 'Orange'],['Pink', 'Purple']];
//attempting to use nested arrays to get each string from an array
function getString(arr){
//this loop should grab each array in the list of arrays
for (let i = 0; i < arr.length; i++){
console.log(i , arr[i]);
//this should assign each sub array to a new var to be iterated over
subArr = arr[i];
} for (let j = 0; j < subArr.length; j++){
console.log(j, arr[j]);
}
};
console.log(getString(pairs));
the problem is the output is of the last for loop is : ['Pink', 'Purple'] not each color extracted from the nested loops.
What am I doing wrong here?
Mirii
You should nest the for loops like this:
for (let i = 0; i < arr.length; i++) {
console.log(i, arr[i]);
//this should assign each sub array to a new var to be iterated over
subArr = arr[i];
for (let j = 0; j < subArr.length; j++) {
console.log(j, arr[j]);
}
}
How you have it, they'd run one after the other.
The solution is provided
:
function getString(arr) {
let arrResult = [];
for (let i = 0; i < arr.length; i++) {
for (let j = 0; j < arr[i].length; j++) {
arrResult.push(arr[i][j]);
}
}
return arrResult;
}
You need to nest the loops, just like you are nesting the arrays. Also, unless you want to alter i or j, I suggest you use .forEach as it is more simple to work with.
Example:
pairs.forEach((pair, i) => {
pair.forEach((subPair, j) => {
console.log(j, subPair);
});
});
You may also make a variable, push to it within the pair.forEach function, and return it at the end of your root function.
I hope this answers your question, thank you for posting, and have a nice day. ;P
Your loops aren't actually nested: you close the first loop before starting the second one. Because subArr is a global varialbe (no let, const, or var keyword), it's still defined in the second loop, but that's not an ideal way to do things. You also need to log arr[i][j] rather than what you have.
This fixes those issues:
function getString(arr) {
//this loop should grab each array in the list of arrays
for (let i = 0; i < arr.length; i++){
//this should assign each sub array to a new var to be iterated over
let subArr = arr[i];
for (let j = 0; j < subArr.length; j++){
console.log(arr[i][j]);
}
}
};
getString(pairs);
Another issue you have is that you're calling console.log(getString(pairs)), but getString doesn't return anything, it's logging itself. If you want it to return, for example, a newline-delimited string of all the items, you could push items to an array and return them joined with a newline (or whatever character you want):
function getString(arr) {
let ret = []
//this loop should grab each array in the list of arrays
for (let i = 0; i < arr.length; i++){
//this should assign each sub array to a new var to be iterated over
let subArr = arr[i];
for (let j = 0; j < subArr.length; j++){
ret.push(arr[i][j]);
}
}
return ret.join('\n')
};
console.log(getString(pairs));
Nested loops themselves aren't ideal, since they're not as readable as using array methods. Using forEach takes much less code:
function getString (arr) {
arr.forEach(function (subArr) {
console.log(subArr[0])
console.log(subArr[1])
})
}
getString(pairs)
Or, more succinctly, you can use map:
function getString (arr) {
return arr.map(([ a, b ]) => `${a}\n${b}`).join('\n');
}
console.log(getString(pairs))
Even more succinctly, you can do this with [].flat():
const getString = (xs = []) => xs.flat().join('\n')
console.log(getString(pairs))

How to fill multidimensional array in javascript?

I tried to get this to work, but the outer loop stops after second iteration, and everything that's after it does not execute(just like it was the end of the script). I want to fill two dimensional array with any character(here i used 'q' as an example)
var A=[[],[]];
for(var i=0;i<12;i++){
for(var j=0;j<81;j++){
A[i][j]='q';
}
}
It didn't work, so i put alert(i+' '+j); to see if it's even executing, and, as i wrote before, it stops after second iteration of outer loop, and then ignores rest of the script.
All I want is to have this array filled with same character in the given range(12 rows, 81 columns in this specific case), so if there's no hope in this method, i'll be glad to see one that works.
This does the job in one line.
var A = Array(12).fill(null).map(()=>Array(81).fill('q'))
This is an array of references and a bad idea as harunurhan commented.
var A = Array(12).fill(Array(81).fill('q'));
The Array.from() method creates a new, shallow-copied Array instance
from an array-like or iterable object.
function createAndFillTwoDArray({
rows,
columns,
defaultValue
}){
return Array.from({ length:rows }, () => (
Array.from({ length:columns }, ()=> defaultValue)
))
}
console.log(createAndFillTwoDArray({rows:3, columns:9, defaultValue: 'q'}))
var A=[[], []];
^ This line declares a two dimensional array of size 1x2. Try this instead:
var A = [];
for (var i = 0; i < 12; i++) {
A[i] = [];
for (var j = 0; j < 81; j++) {
A[i][j] = 'q';
}
}
Since fill() is the most succinct and intuitive, and it works as intended for immutable values, my preference would be an outer from() and an inner fill():
Array.from({length: 12}, _ => new Array(81).fill('q'));
The best approach to fill up 2D array would be like the following
let array2D = [], row = 3, col = 3, fillValue = 1
for (let i = 0; i < row; i++){
let temp = []
for (let j = 0; j < col; j++){
temp[j] = fillValue
}
array2D.push(temp)
}
You need to initialise a new array for i each time the first loop runs, and you don't need to set the layout of the array before you create it (Remove the [], [] inside the declaration of A). Try this:
var A = [];
for (var i = 0; i < 12; i++) {
A[i] = [];
for (var j = 0; j < 81; j++) {
A[i][j] = 'q';
}
}
console.log(A);
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max-height: 100% !important;
top: 0;
}

JavaScript iterate through an object arrays(unknown number of content array)

I am trying to iterate through an object which has unknown number of arrays and also i dont know number of data in each array because im pulling it from a database like this for example.
i can know how many arrays in object with data.length so first for loops condition will be data.length but because i dont know how many data in each array how can i decide second for loop condition ? thanks
for(var i = 0; i <= data.length; i++) {
for(var k = 0; k <= ????; k++) {
data[i][k].locationlat
}
}
So you want to iterate through a 2-dimensional array? Would something like this work?
var num_d1 = data.length;
for (var i=0; i<num_d1; i++) {
var num_d2 = data[i].length;
for (var k=0; k<num_d2; k++) {
console.log('Latitude: ', data[i][k].locationlat)
}
}

Compare two arrays in javascript

I'd like to check which elements are equal in my two arrays, but can't get it working.
This is my code:
for (var i; i < bombs.length; i++) {
for (var j; j < bombsDb.length; j++) {
if (bombs[i].name === bombsDb[j].address) {
console.log(bombs[i].name);
} else {
console.log("non-equal elements");
}
}
}
So the first array contains objects from the google places api and the second one contains data from my database.
Thanks in advance!
You have to initialize i and j;
for (var i = 0; i < bombs.length; i++) {
for (var j = 0; j < bombsDb.length; j++) {
if (bombs[i].name === bombsDb[j].address) {
console.log(bombs[i].name);
} else {
console.log("non-equal elements");
}
}
}
Comparing can also be done using the .not selector from jquery. Check this:
var a = [1,2,3,4,5,6];
var b = [4,5,6,7,8,9];
$(a).not( $(a).not(b).get() ).get();
This will return the following array
[4,5,6]
You are missing the initial assignment to i and j in your for loop.
// here
// v
for (var i = 0; i < bombs.length; i++) {
// your loop
}
This causes the comparision to return false in the first iteration of the loop since undefined < bombs.length always return false, so it will not proceed.

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