This question already has answers here:
Initializing an Array with a Single Value
(12 answers)
Closed 8 years ago.
I want to make a new array (of X elements) with all the elements set to 0.
X is set before.
Anyone could make the most compact and easy code for that? Thank you for your
help.
Just create a function:
function makeArray(size, defaultValue) {
var arr = [];
for (var i = 0; i < size; i++) arr.push(defaultValue);
return arr;
}
var myArr = makeArray(10, 0);
Related
This question already has answers here:
How to create an array containing 1...N
(77 answers)
Closed 20 days ago.
how creating a JavaScript array containing 1 through to x where x is only known at runtime without the loop.
var arr = [];
for (var i = 1; i <= x; i++) {
arr.push(i);
}
This is a duplicate of this issue
here is the answer anyway
const arr = [...''.padEnd(N)].map((_,i)=>i+1)
This question already has answers here:
How to create an array containing 1...N
(77 answers)
Fastest way to fill an array with multiple value in JS. Can I pass a some pattern or function to method fill insted of a single value in JS? [duplicate]
(1 answer)
Closed 4 years ago.
I want to create a function that takes input from user and returns an array with all the numbers from 1 to the passed number as an argument. Example: createArray(10) should return [1,2,3,4,5,6,7,8,9,10]. I came up with this solution:
function createArray(input) {
var value = 0;
var array = [];
for (i=0;i<input;i++) {
value++;
array.push(value)
console.log(array)
}
}
createArray(12);
What is the correct and better way of doing it?
I would prefer to use Array.from:
const createArray = length => Array.from(
{ length },
// Mapper function: i is the current index in the length being iterated over:
(_, i) => i + 1
)
console.log(JSON.stringify(createArray(10)));
console.log(JSON.stringify(createArray(5)));
There is no need for the extra variable just do this:
function createArray(input) {
var array = [];
for (i = 0; i <= input; i++) {
array.push(i);
}
return array;
}
This question already has answers here:
Array.fill(Array) creates copies by references not by value [duplicate]
(3 answers)
Closed 4 years ago.
I tried to create a 2-dimensional array in javascript. (Actually, the code is written in typescript and will be used to style DOM Elements with Angular2 but, as far as I am concerned, it shouldn't have any effect on the result in this case.)
First way:
arrayi = Array(10).fill(Array(20).fill(-1))
Second way:
array = [];
for(var i: number = 0; i < 10; i++) {
array[i] = [];
for(var j: number = 0; j< 20; j++) {
array[i][j] = -1;
}
}
If I call array[1][2] = 2; it does what I expected, what means setting one element in the 2-dimensional array to 2.
However, if I call arrayi[1][2] = 2; every element arrayi[x][2] will be set to 2. (With x element {0,1,2,...,9})
Why is that? I don't understand it. So it would be nice if someone could explain it to me.
The arrays are defined as array: number[][] and arrayi: number[][] in typescript.
arrayi = Array(10).fill(Array(20).fill(-1)) fills with the same array.
You can even rewrite it like this
const arr1 = Array(20).fill(-1)
const arrayi = Array(10).fill(arr1)
console.log(arrayi.every(item => item === arr1)) //true
The reason is that you create one instance of array with 20 elements and put this single instance into each element of root array
This question already has answers here:
Javascript array length incorrect on array of objects
(3 answers)
Closed 8 years ago.
I don't understand why is array so strange when I add element by key.
For example:
var test = new Array();
test['a'] = 'aaa';
test['b'] = 'bbb';
test.length == 0; // true. Why?
And when I run:
test.map(function(el){
console.log(el);
});
// nothing print. Why?
When I add element with push method everything works OK. Thanks
Arrays in javascript are not associative, you can't set keys like that i.e.
var test = [];
test.push('aaa');
test.push('bbb');
// OR
test[0] = 'aaa';
test[1] = 'bbb';
test.length = 2
This question already has answers here:
Closed 10 years ago.
Possible Duplicate:
Sorting JavaScript Object by property value
Sort JavaScript object by key
I've written a function called frequency() that takes an Array, counts the number of times a string is found within it, and then returns an object based on these results.
Code:
var array = ["Diesel","Asos","Diesel","Paul Smith"];
function frequency(array) {
var frequency = {}, value;
for(var i = 0; i < array.length; i++) {
value = array[i];
if(value in frequency)
frequency[value]++;
else
frequency[value] = 1;
}
return frequency;
}
ordered = frequency(array);
Sample output:
{"Asos":1,"Diesel":2,"Paul Smith":1}
How can I now sort this outputted object based on the counted frequency value?