Remove empty elements from an array in Javascript

I needed to do this same task and came upon this thread. I ended up using the array "join" to create a string using a "_" separator, then doing a bit of regex to:-

1. replace "__" or more with just one "_",
2. replace preceding "_" with nothing "" and similarly 
3. replace and ending "_" with nothing ""

...then using array "split" to make a cleaned-up array:-

var myArr = new Array("","","a","b","","c","","","","","","","","","e","");
var myStr = "";

myStr = myArr.join("_");

myStr = myStr.replace(new RegExp(/__*/g),"_");
myStr = myStr.replace(new RegExp(/^_/i),"");
myStr = myStr.replace(new RegExp(/_$/i),"");
myArr = myStr.split("_");

alert("myArr=" + myArr.join(","));

...or in 1 line of code:-

var myArr = new Array("","","a","b","","c","","","","","","","","","e","");

myArr = myArr.join("_").replace(new RegExp(/__*/g),"_").replace(new RegExp(/^_/i),"").replace(new RegExp(/_$/i),"").split("_");

alert("myArr=" + myArr.join(","));

...or, extending the Array object :-

Array.prototype.clean = function() {
  return this.join("_").replace(new RegExp(/__*/g),"_").replace(new RegExp(/^_/i),"").replace(new RegExp(/_$/i),"").split("_");
};

var myArr = new Array("","","a","b","","c","","","","","","","","","e","");

alert("myArr=" + myArr.clean().join(","));

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

If using a library is an option I know underscore.js has a function called compact() http://documentcloud.github.com/underscore/ it also has several other useful functions related to arrays and collections.

Here is an excerpt from their documentation:

_.compact(array)

Returns a copy of the array with all falsy values removed. In JavaScript, false, null, 0, "", undefined and NaN are all falsy.

_.compact([0, 1, false, 2, '', 3]);

=> [1, 2, 3]

If you need to remove ALL empty values ("", null, undefined and 0):

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

Example:

arr = ["hello",0,"",null,undefined,1,100," "]  
arr.filter(function(e){return e});

Return:

["hello", 1, 100, " "]

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]

or

arr = arr.filter(Number)

via jQuery:

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

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

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

The clean way to do it.

var arr = [0,1,2,"Thomas","false",false,true,null,3,4,undefined,5,"end"];
arr = arr.filter(Boolean);
// [1, 2, "Thomas", "false", true, 3, 4, 5, "end"]

What about that:

js> [1,2,,3,,3,,,0,,,4,,4,,5,,6,,,,].filter(String).join(',')
1,2,3,3,0,4,4,5,6

@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;
  };
}

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]
*/

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.

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... ;)

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;
}

You'll have to loop and then splice()

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