Remove empty elements from an array in Javascript

Question

How do I remove empty elements from an array in Javascript? Is there a straightforward way, or do I need to loop through it and remove them manually?

Thanks

Answer 1

You'll need use some form of iteration to accomplish this. There isn't any built in mechanism in JavaScript to accomplish the task.

Answer 2

You'll have to loop and then splice()

Answer 3

Try this. Pass it your array and it will return with empty elements removed. *Updated to address the bug pointed out by Jason

function removeEmptyElem(ary) {
    for (var i=ary.length;i>=0;i--) {
        if (ary[i] == undefined)  {
            ary.splice(i, 1);
        }    
    }
    return ary;
}

Answer 4

You may find it easier to loop over your array and build a new array out of the items you want to keep from the array than by trying to loop and splice as has been suggested, since modifying the length of the array while it is being looped over can introduce problems.

You could do something like this:

function removeFalsyElementsFromArray(someArray) {
    var newArray = [];
    for(var index = 0; index < someArray.length; index++) {
        if(someArray[index]) {
            newArray.push(someArray[index]);
        }
    }
    return newArray;
}

Actually here is a more generic solution:

function removeElementsFromArray(someArray, filter) {
    var newArray = [];
    for(var index = 0; index < someArray.length; index++) {
        if(filter(someArray[index]) == false) {
            newArray.push(someArray[index]);
        }
    }
    return newArray;
}

// then provide one or more filter functions that will 
// filter out the elements based on some condition:
function isNullOrUndefined(item) {
    return (item == null || typeof(item) == "undefined");
}

// then call the function like this:
var myArray = [1,2,,3,,3,,,,,,4,,4,,5,,6,,,,];
var results = removeElementsFromArray(myArray, isNullOrUndefined);

// results == [1,2,3,3,4,4,5,6]

You get the idea - you could then have other types of filter functions. Probably more than you need, but I was feeling generous... ;)

Answer 5

I use this method, extending the native Array prototype:

Array.prototype.clean = function(deleteValue) {
  for (var i = 0; i < this.length; i++) {
    if (this[i] == deleteValue) {         
      this.splice(i, 1);
      i--;
    }
  }
  return this;
};

test = new Array("","One","Two","", "Three","","Four").clean("");

test2 = [1,2,,3,,3,,,,,,4,,4,,5,,6,,,,];
test2.clean(undefined);

Or you can simply push the existing elements into other array:

function cleanArray(actual){
  var newArray = new Array();
  for(var i = 0; i<actual.length; i++){
      if (actual[i]){
        newArray.push(actual[i]);
    }
  }
  return newArray;
}

cleanArray([1,2,,3,,3,,,,,,4,,4,,5,,6,,,,]);

Answer 6

If you've got Javascript 1.6 or later you can use Array.filter using a function similar to the isNullOrUndefined function in Jason's answer. See:

https://developer.mozilla.org/en/Core_JavaScript_1.5_Reference/Objects/Array/filter

This page also contains a nice error-checking version of filter that can be used in JavaScript interpreters that don't support the official version.

Answer 7

This works, I tested it in AppJet (you can copy-paste the code on its IDE and press "reload" to see it work, don't need to create an account)

/* appjet:version 0.1 */
function Joes_remove(someArray) {
    var newArray = [];
    var element;
    for( element in someArray){
        if(someArray[element]!=undefined ) {
            newArray.push(someArray[element]);
        }
    }
    return newArray;
}

var myArray2 = [1,2,,3,,3,,,0,,,4,,4,,5,,6,,,,];

print("Original array:", myArray2);
print("Clenased array:", Joes_remove(myArray2) );
/*
Returns: [1,2,3,3,0,4,4,5,6]
*/

Answer 8

@Alnitak

Actually Array.filter works on all browsers if you add some extra code. See below.

var array = ["","one",0,"",null,0,1,2,4,"two"];

function isempty(x){
if(x!=="")
    return true;
}
var res = array.filter(isempty);
document.writeln(res.toJSONString());
// gives: ["one",0,null,0,1,2,4,"two"]

This is the code you need to add for IE, but filter and Functional programmingis worth is imo.

//This prototype is provided by the Mozilla foundation and
//is distributed under the MIT license.
//http://www.ibiblio.org/pub/Linux/LICENSES/mit.license

if (!Array.prototype.filter)
{
  Array.prototype.filter = function(fun /*, thisp*/)
  {
    var len = this.length;
    if (typeof fun != "function")
      throw new TypeError();

    var res = new Array();
    var thisp = arguments[1];
    for (var i = 0; i < len; i++)
    {
      if (i in this)
      {
        var val = this[i]; // in case fun mutates this
        if (fun.call(thisp, val, i, this))
          res.push(val);
      }
    }

    return res;
  };
}

Answer 9

array=array.fitler(/\w/); filter + regexp

Answer 10

Pure javascript:

var arr = [1,2,,3,,3,,,0,,,4,,4,,5,,6,,,,];

arr = arr.filter(function(){ return true});

arr // [1, 2, 3, 3, 4, 4, 5, 6]

via jQuery:

var arr = [1,2,,3,,3,,,0,,,4,,4,,5,,6,,,,];

arr = $.grep(arr,function(n,i){
    return(n);
});

arr // [1, 2, 3, 3, 4, 4, 5, 6]