Need to reset just the indexes of a Javascript array

Question

I have a for loop which returns an array.

Return:

1st loop:
arr[0]
arr[1]
arr[2]
arr[3]

Here the length I get is 4 (Not a problem).

Return:

2nd loop
arr[4]
arr[5]
arr[6]
arr[7] 
arr[8]

Here the length I get is 9.

What I want here is the actual count of the indexes i.e I need it to be 5. How can I do this. And is there a way that when I enter each loop every time it starts from 0 so that I get proper length in all the loops?

You need to show us the loop you are using, the condition inside it and the initialisation of your array in the first place. — Dan Prince, Jul 10 '12 at 13:05

score 39 · Answer 1 · answered Dec 14 '13 at 18:28

39

This is easily done natively using Array.filter:

resetArr = orgArr.filter(function(){return true;});

answered Dec 14 '13 at 18:28

Dag Sondre Hansen

2,449
20
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2

Worked perfect for me! – Emmanuel Mar 17 '14 at 00:38
1

+1 clean solution. It works even using the same array: origArr = origArr.filter(...) – lepe Mar 25 '14 at 04:03
Note that this will not work for IE <= 8. You may implement this suggested polyfill to solve that problem: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/filter – Dag Sondre Hansen May 20 '14 at 06:08
2

Bit shorter version : resetArr = orgArr.filter(Boolean); – M_R_K May 12 '19 at 23:04

danmcardle · Answer 2 · 2012-07-10T13:19:07.007

4

You could just copy all the elements from the array into a new array whose indices start at zero.

E.g.

function startFromZero(arr) {
    var newArr = [];
    var count = 0;

    for (var i in arr) {
        newArr[count++] = arr[i];
    }

    return newArr;
}

// messed up array
x = [];
x[3] = 'a';
x[4] = 'b';
x[5] = 'c';

// everything is reordered starting at zero
x = startFromZero(x);

edited Jul 10 '12 at 13:19

answered Jul 10 '12 at 13:13

danmcardle

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i love you crazedgremlin..you made my day – Adnan Baliwala Jul 10 '12 at 14:15
1

You're welcome! Just so you know, this is a bad solution to your problem -- you should probably choose a new data structure such as a linked list that will allow you to delete items without having to recreate the array each time. Also, you should choose an answer if you have found a solution to your problem! – danmcardle Jul 10 '12 at 14:42

score 4 · Answer 3 · answered Mar 08 '19 at 14:38

4

Easy,

var filterd_array = my_array.filter(Boolean);

answered Mar 08 '19 at 14:38

M_R_K

5,929
1
39
40

score 3 · Answer 4 · edited Sep 19 '19 at 17:48

3

Perhaps "underscore.js" will be useful here.

The _.compact() function returns a copy of the array with no undefined.

See: http://underscorejs.org/#compact

edited Sep 19 '19 at 17:48

ata

3,398
5
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answered Apr 16 '13 at 19:18

hallodom

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awesome lib ; applies to arrays and also avoid removal of non empty objects. – Victor Oliveira Apr 25 '20 at 16:20

Need to reset just the indexes of a Javascript array

4 Answers4

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