Remove empty elements from an array in Javascript

A few simple ways:

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

arr.filter(n => n)
// [1, 2, 3, -3, 4, 4, 5, 6]

arr.filter(Number) 
// [1, 2, 3, -3, 4, 4, 5, 6]

arr.filter(Boolean) 
// [1, 2, 3, -3, 4, 4, 5, 6]

or - (only for single array items of type "text")

['','1','2',3,,'4',,undefined,,,'5'].join('').split(''); 
// output:  ["1","2","3","4","5"]

or - Classic way: simple iteration

var arr = [1,2,null, undefined,3,,3,,,0,,,[],,{},,5,,6,,,,],
    len = arr.length, i;

for(i = 0; i < len; i++ )
    arr[i] && arr.push(arr[i]);  // copy non-empty values to the end of the array

arr.splice(0 , len);  // cut the array and leave only the non-empty values
// [1,2,3,3,[],Object{},5,6]

jQuery:

var arr = [1,2,,3,,3,,,0,,,4,,4,,5,,6,,,,];
    
arr = $.grep(arr, n => n == 0 || n);
// [1, 2, 3, 3, 0, 4, 4, 5, 6]

Simply one liner:

[1, false, "", undefined, 2].filter(Boolean); // [1, 2]

or using underscorejs.org:

_.filter([1, false, "", undefined, 2], Boolean); // [1, 2]
// or even:
_.compact([1, false, "", undefined, 2]); // [1, 2]

EDIT: This question was answered almost nine years ago when there were not many useful built-in methods in the Array.prototype.

Now, certainly, I would recommend you to use the filter method.

Take in mind that this method will return you a new array with the elements that pass the criteria of the callback function you provide to it.

For example, if you want to remove null or undefined values:

var array = [0, 1, null, 2, "", 3, undefined, 3,,,,,, 4,, 4,, 5,, 6,,,,];

var filtered = array.filter(function (el) {
  return el != null;
});

console.log(filtered);

It will depend on what you consider to be "empty" for example, if you were dealing with strings, the above function wouldn't remove elements that are an empty string.

One typical pattern that I see often used is to remove elements that are falsy, which include an empty string "", 0, NaN, null, undefined, and false.

You can pass to the filter method, the Boolean constructor function, or return the same element in the filter criteria function, for example:

var filtered = array.filter(Boolean);

Or

var filtered = array.filter(function(el) { return el; });

In both ways, this works because the filter method in the first case, calls the Boolean constructor as a function, converting the value, and in the second case, the filter method internally turns the return value of the callback implicitly to Boolean.

If you are working with sparse arrays, and you are trying to get rid of the "holes", you can use the filter method passing a callback that returns true, for example:

var sparseArray = [0, , , 1, , , , , 2, , , , 3],
    cleanArray = sparseArray.filter(function () { return true });

console.log(cleanArray); // [ 0, 1, 2, 3 ]

Old answer: Don't do this!

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:

// Will remove all falsy values: undefined, null, 0, false, NaN and "" (empty string)
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,,,,]);

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

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

To remove empty values and Line breaks:

arr = arr.filter(function(e){ return e.replace(/(\r\n|\n|\r)/gm,"")});

Example:

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

Return:

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

UPDATE (based on Alnitak's comment)

In some situations you may want to keep "0" in the array and remove anything else (null, undefined and ""), this is one way:

arr.filter(function(e){ return e === 0 || e });

Return:

["hello", 0, 1, 100, " "]