how to remove null, undefined, NaN, 0s, falses and empty string from an array in JavaScript?

Question

I wrote a script to remove any null, undefined, 0, false or empty string value using .splice(), but the code has only removed NaN and 0s.

Here is what I tried:

function remove(arr){ // input [NaN, 0, 15, false, -22, '',undefined, 47, null]
    var bin = [];
    for (var i =0; i<arr.length; i++){
        if (arr[i] == (NaN || 0 || false || "" || undefined || null)){
            arr.splice(arr[i],1);
        }
    }
  console.log(arr); // Expected output [15, -22, 47]
}

Answer 1

Problem in code:

1. Iterate over array from last element to first element
2. Array#splice expects first argument as index, not the item itself
3. To check if an element is NaN , use isNaN() .
4. To compare with multiple values, compare the elements individually with each item

Working code:

 function remove(arr) { for (var i = arr.length - 1; i >= 0; i--) { if (isNaN(arr[i]) || arr[i] === 0 || arr[i] === false || arr[i] === "" || arr[i] === undefined || arr[i] === null) { // Which is same as // if (!arr[i]) { arr.splice(i, 1); } } console.log(arr); // Expected output [15, -22, 47] } remove([NaN, 0, 15, false, -22, '', undefined, 47, null]);

---

Use Array#filter

arr = arr.filter(e => e);

 var input = [NaN, 0, 15, false, -22, '',undefined, 47, null]; var filteredArr = input.filter(e => e); document.body.innerHTML = '<pre>' + JSON.stringify(filteredArr, 0, 4) + '</pre>';

Or as said by @dandavis in comment

arr = arr.filter(Boolean);

 var input = [NaN, 0, 15, false, -22, '',undefined, 47, null]; var filteredArr = input.filter(Boolean); document.body.innerHTML = '<pre>' + JSON.stringify(filteredArr, 0, 4) + '</pre>';

Answer 2

This solution may not be that efficient

function filterArray(el) {
    return (typeof (el) === "number" && el != 0 && !isNaN(el));
}

arr = [NaN, 0, 15, false, -22, '', undefined, 47, null];
console.log(arr.filter(filterArray));

jsfiddle

Answer 3

使用lodash 。

console.log(_.compact(arr));

Answer 4

You refer to using splice so I assume you want an in-place (mutating) solution. Here's a simple, quick approach:

function compact(a) {
  var i = 0, j = 0;

  while (i < a.length) {
    var v = a[i++];
    if (v) a[j++] = v;
  }

  a.length = j;
}

In case you care (and you probably shouldn't), this is 10 times faster than a loop over splice . See http://jsperf.com/compacting-an-array .

If you want a solution which creates a new array, the alternatives given in other answers using filter are fine, but here's a basic version:

function compact(a) {
  var i = 0, j = 0, result = [];

  while (i < a.length) {
    var v = a[i++];
    if (v) result[j++] = v;
  }

  return result;
}

Answer 5

 function bouncer(arr) {
  var newArr=arr.slice(0);
  var n=0;
  for(var i=0; i<arr.length;i++){
    if(arr[i]==false||arr[i]==null||arr[i]==0||arr[i]==""||arr[i]==undefined||Number.isNaN(arr[i])==true){
      newArr.splice(n,1);

    } else n++;
  }
  console.log(newArr);
  return newArr;
}

bouncer([null, NaN, 1, 2, undefined,0,'a']);

I have tried to do it with slice()... For NaN I used the function Number.isNaN() and if returns true goes on... The input was [null, NaN, 1, 2, undefined,0,'a'] and returned [ 1, 2, 'a'] as it is expected... Hope it helped you