How to create an array in JS that is initialized to 0?

Question

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Most efficient way to create a zero filled JavaScript array?

I wish to create an array in JS, the array will store integer value.

I would like to increment some of the values by 1, o at first I would like that each cell in the array would contain 0

Is it possible to do it in JS ?

Note: The array is of unknown size upon creation

@AndreasKöberle - Please note that in my question the array size is unknown — Belgi, Jan 18 '13 at 07:36
Did you mean to say that this multidimensional array, and you want to initialize each element inside to 0 so that you can increment each item without getting the undefined problem? If so, then you'll want to edit this question to explain that better, as well as the title, and then flag a moderator to request reopening this question as a separate question than the one they think is a duplicate. — Volomike, Sep 04 '19 at 01:03

gurvinder372 · Answer 1 · 2013-01-18T07:31:55.213

2

var arr = [0,0,0,0];

incrementIndex(1,0);
incrementIndex(2,1);

function incrementIndex(index, value)
{
  arr[ index ] = arr[ index ] + value;


}

Edit:

var arr = returnArray(10);

function returnArray(numberofIndexes)
{
  var arr = new Array();
  for ( var counter = 0; counter < numberOfIndexes; counter++)
  {
     arr.push(0);
  }
  return arr;
}

edited Jan 18 '13 at 07:31

answered Jan 18 '13 at 07:23

gurvinder372

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But this does not create an array of unknown size... – Belgi Jan 18 '13 at 07:26
@Belgi updated the code. please check now – gurvinder372 Jan 18 '13 at 07:30
Thanks, but "numberofIndexes" is not known – Belgi Jan 18 '13 at 07:43
@belgi You just need to give an initial value, you can always expand the array later. – gurvinder372 Jan 18 '13 at 07:46

SangYeob Bono Yu · Accepted Answer · 2013-01-18T07:29:44.940

1

Array.prototype.increaseAt = function(index){
    this[index] = this[index]+1 || 1
};
Array.prototype.getValueAt = function(index){
    return this[index] || 0;
};

Use it like:

var testArray = [];
testArray.increaseAt(3);
console.log(testArray.getValueAt(3)); // 1
console.log(testArray.getValueAt(1)); // 0

edited Jan 18 '13 at 07:29

answered Jan 18 '13 at 07:21

SangYeob Bono Yu

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4
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Yes, this should be 0. Can I make it print 0 ? thanks for the help! – Belgi Jan 18 '13 at 07:26
@Belgi I edited answer... not so good approach, but maybe you can use it. – SangYeob Bono Yu Jan 18 '13 at 07:31
Thanks! by the way: I can just use "Array.prototype..." just like this or do I need to include something (like in C/C++) ? – Belgi Jan 18 '13 at 07:35
@Belgi You don't need to include anything. Array is built-in class. – SangYeob Bono Yu Jan 18 '13 at 07:38
2

Messing with the prototypes of Array, Date, etc. is not a good practice. Even for a short piece of code... if it's short, a separated function to this wouldn't hurt. – istepaniuk Jan 18 '13 at 07:41

score -1 · Answer 3 · answered Jan 18 '13 at 07:33

-1

You can access item of array by index of this item, like this item[index] += 1

answered Jan 18 '13 at 07:33

Stiger

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How to create an array in JS that is initialized to 0?

3 Answers3