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

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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]
}

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]
}

• javascript
• arrays

Share Improve this question Follow edited Mar 18, 2016 at 7:22 user663031 asked Mar 18, 2016 at 4:24 Mohamed HegazyMohamed Hegazy 27344 silver badges1818 bronze badges 5

• 3 arr = arr.filter(e => e); – Tushar Commented Mar 18, 2016 at 4:24
• 2 arr = arr.filter(Boolean) is built-in ES5. – dandavis Commented Mar 18, 2016 at 4:25
• Possibly duplicate stackoverflow./questions/31925323/… – brk Commented Mar 18, 2016 at 4:41
• Where did you find the syntax x == (a || b || c || d) and what do you expect it to do? Why are you trying to use splice instead of using filter to create a new array? – user663031 Commented Mar 18, 2016 at 4:53
• I was trying to check if x is equal to a or b or c or d, I can tell from your ment that it's wrong syntax, would you please explain why? I was using splice because I am new to programming so I didn't know any better – Mohamed Hegazy Commented Mar 23, 2016 at 3:10

Add a ment  | 

5 Answers 5

Sorted by: Reset to default 3

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 pare with multiple values, pare 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 ment

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>';

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

use lodash.

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

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

function pact(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./pacting-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 pact(a) {
  var i = 0, j = 0, result = [];

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

  return result;
}

 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

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