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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?

2020/08/24
1
1192
8/24/2020 8:58:11 PM

Accepted Answer

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,,,,]);
1136
8/21/2019 12:02:59 PM


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, " "]
2018/05/18

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]
2013/08/14

If you've got Javascript 1.6 or later you can use Array.filter using a trivial return true callback function, e.g.:

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

since .filter automatically skips missing elements in the original array.

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

Note that this will not remove null entries nor entries with an explicit undefined value, but the OP specifically requested "missing" entries.

2014/07/10

For removing holes, you should use

arr.filter(() => true)
arr.flat(0) // Currently stage 3, check compatibility before using this

For removing hole, and, falsy (null, undefined, 0, -0, NaN, "", false, document.all) values:

arr.filter(x => x)

For removing hole, null, and, undefined:

arr.filter(x => x != null)

arr = [, null, (void 0), 0, -0, NaN, false, '', 42];
console.log(arr.filter(() => true)); // [null, (void 0), 0, -0, NaN, false, '', 42]
console.log(arr.filter(x => x)); // [42]
console.log(arr.filter(x => x != null)); // [0, -0, NaN, false, "", 42]

2018/09/19

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"]
2011/03/26

Source: https://stackoverflow.com/questions/281264
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