code designed to remove NaN from array, still returns NaN JS

Question

I need to remove all empty values (null, undefined, '', NaN, false) EXCEPT 0 from an array. eg: [0, false, [], undefined, {}, NaN, 'Kevin'] => [0, [], {}, 'Kevin'];

function removeBlank(array) {
  array = array.filter(function (n) {
    return (n !== undefined && n !== null && n !== false && n !== "" && isNaN()!= NaN); });
  console.log( array );
}

However this still returns a NaN. for example removeBlank([0, NaN, undefined, false, '', null, 'Kevin']); returns [0, NaN, "Kevin"]

How do I improve the isNaN()!= NaN) to remove NaN with out removing strings, ZEROS or other numbers?

ibrahim mahrir · Accepted Answer · 2017-05-14 09:43:52Z

1

isNaN()!= NaN has no meaning, isNaN is a function that takes a parameter and check (return true or false) if it's a valid number or not, you are not passing to it anything.

And even if you use it right, it won't work, because then all values that are not numbers will be filtered out.

I'd suggest using this:

array = array.filter(function (n) {
    return n || n === 0;
});

either n is truthy or it is 0.

edited May 14, 2017 at 9:43

answered May 14, 2017 at 9:37

ibrahim mahrir

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7 Comments

ibrahim mahrir Over a year ago

@MaxES logical OR, it means either side is true or truthy. If n !== false !== "" !== 0 !== NaN !== undefined !== null then it's truthy and then n is equivalent to true so the test is ok. If n === 0 then the left side of || will be equivalent to false, but the right side n === 0 will be true, || need only one true side to be true. So either n is truthy or it is equal to 0.

ibrahim mahrir Over a year ago

@MaxES Here is more about logical operators.

arboreal84 Over a year ago

If it's Infinity or -Infinity it will return true. Usually it is a bad idea to work with infinite numbers, almost no application deals with them.

ibrahim mahrir Over a year ago

@arboreal84 I'm not sure what you are talking about?

ibrahim mahrir Over a year ago

@arboreal84 both Infinity and -Infinity are truthy as they should be.

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arboreal84 · Accepted Answer · 2017-05-14 09:38:39Z

0

isNaN takes the number as a parameter. Needs to be isNaN(n)

Then, unless you want to work with infinite numbers, like -Infinity and Infinity, I recommend you just validate with:

arr.filter(function (n) {
   return isFinite(n);
});

NaN is not finite so it would be filtered too. NaN also has the property that any comparison will make it return false. This means n == n will return false if n is NaN.

answered May 14, 2017 at 9:38

arboreal84

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2 Comments

ibrahim mahrir Over a year ago

Infinity should be truthy. I guess.

arboreal84 Over a year ago

Infinity is not a number that you can operate with other numbers other than for the purposes of comparison. In that sense, Infinity almost always breaks business logic.

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