Fill empty array

Question

I need to iterate from 0 to 30, but I want to do this with help of forEach:

new Array(30).forEach(console.log.bind(console);

Of course this does not work, therefor I do:

new Array(30).join(',').split(',').forEach(console.log.bind(console));

Is there other ways to fill empty arrays?

Use for loop instead. – Mike Grabowski Apr 29 '14 at 09:05 — Mike Grabowski, Apr 29 '14 at 09:05

score 4 · Accepted Answer · answered Apr 29 '14 at 09:10

Actually, there's a simple way to create a [0..N) (i.e., not including N) range:

var range0toN = Object.keys(Array.apply(0,Array(N)));

Apparently Object.keys part can be dropped if you only want to get a proper array of N elements.

Still, like others said, in this particular case it's probably better to use for loop instead.

score 2 · Answer 2 · answered Aug 18 '21 at 04:25

2

if you want all of item have same value, do this

var arrLength = 4
var arrVal = 0

var newArr = [...new Array(arrLength)].map(x => arrVal);
// result will be [0, 0, 0, 0]

answered Aug 18 '21 at 04:25

Roby Cigar

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score 0 · Answer 3 · edited May 23 '17 at 12:07

0

If you simply want to iterate, then use for loop like this

for (var i = 0; i < 30; i += 1) {
    ...
    ...
}

Actually, if you are looking for a way to create a range of numbers, then you can do

console.log(Array.apply(null, {length: 30}).map(Number.call, Number));

It will create numbers from 0 to 29. Source : Creating range in JavaScript - strange syntax

edited May 23 '17 at 12:07

Community

1
1

answered Apr 29 '14 at 09:07

thefourtheye

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Haha =) I know about common for/white, but I prefer to work with forEach - it provide best encapsulation of code (speed is not important) – 3y3 Apr 29 '14 at 09:11
@3y3 What exactly you are trying to do? What should be the output? – thefourtheye Apr 29 '14 at 09:12
@3y3 Does the updated answer, look fine to you? It is a neat hack ;-) – thefourtheye Apr 29 '14 at 09:20
based on answer of @raina77ow I can propose ```console.log(Array.apply(null, new Array(30)).map(Number.call, Number));```. Length trick is also interesting. Thanks. – 3y3 Apr 29 '14 at 09:42
@3y3 Read the linked question to have a deeper understanding of how that works. I must say, its really worth reading :-) – thefourtheye Apr 29 '14 at 09:44

score 0 · Answer 4 · answered Apr 29 '14 at 09:09

You could try using a for loop. new Array is not a best practise

    var index,      // we use that in the for loop
        counter,    // number of elements in array
        myArray;    // the array you want to fill

    counter = 30;
    myArray = [];

    for (index = 0; index < counter; index += 1) {

        myArray[index] = [];
        /* 
        // alternative:
        myArray.push([]);
        // one-liner
        for (index = 0; index < counter; index += 1) myArray.push([]);
        */
    }

score -2 · Answer 5 · answered Apr 29 '14 at 09:17

-2

If you insist foreach

var data = [1, 2, 3];
data.forEach(function(x) {
    console.log(x);
});

answered Apr 29 '14 at 09:17

jhyap

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Fill empty array

5 Answers5