How can I "reset" an array's keys?

Question

If I have an array and I delete certain elements, I end up with an array that has non-consecutive keys:

var arr = [15,16,20,21,-1];
delete arr[1];
delete arr[3];
console.log(arr);
// [0: 15, 2: 20, 4: -1]

How can I "reset" the array's keys?

I should end up with an array like so:

[0: 15, 1: 20, 2: -1]

This does not look like an array, and the requirement are unclear. — Kyll, Dec 23 '15 at 10:52
I was describing an array, yes. Sorry if the way I output it confused my meaning! — Codemonkey, Dec 23 '15 at 11:20
Just don't use the first answer on that duplicate, extending native objects is an extremely bad thing to do. — , Dec 24 '15 at 00:48

score 8 · Accepted Answer · answered Dec 23 '15 at 10:24

8

For example, you can use Array.prototype.filter method.

var array = [];
array[30] = 1;
array.length; // 31

var compactArray = array.filter(function (item) {
    return item !== undefined;
});

compactArray.length; // 1

If it's an object, for..in loop will be usefull

var array = { 31: 1};
var compactArray = [];
for (var i in array) {
    compactArray.push(array[i]);
}

answered Dec 23 '15 at 10:24

Martin Schulz

582
1
3
13

Thanks, array.filter seems like the cleanest solution. – Codemonkey Dec 23 '15 at 11:19

score 1 · Answer 2 · answered Dec 23 '15 at 10:24

You can loop throw array and if its a valid item, then push in another array.

Also, when you do something like this,

var arr = [];
arr[3] = 15;

arr is actually [null, null, null, 15]

Following is an example.

(function() {
  var arr = [];
  var result = [];

  arr[3] = 15;
  arr[7] = 20;
  arr[19] = -1;

  console.log(arr);
  console.log(JSON.stringify(arr))

  arr.forEach(function(item) {
    if (item) {
      result.push(item);
    }
  })

  console.log(result);
  console.log(JSON.stringify(result));
})()

gurvinder372 · Answer 3 · 2015-12-23T10:20:25.877

0

if you mean your object is like this

var obj = {3: 15, 7: 20, 19: -1};
var output = {};
var counter = 0;
for ( var id in obj )
{
   output[ String( counter ) ] = obj[ id ];
   counter++;
}
console.log( output );

edited Dec 23 '15 at 10:20

answered Dec 23 '15 at 10:18

gurvinder372

66,980
10
72
94

How can I "reset" an array's keys?

3 Answers3