Index 28:

How do I remove this "NaN" value. Cant use isNaN because I want strings and numbers. But not NaN

Tried:

typeof value === 'undefined'
value == null

No success.

Index 28:

How do I remove this "NaN" value. Cant use isNaN because I want strings and numbers. But not NaN

Tried:

typeof value === 'undefined'
value == null

No success.

• javascript
• nan

4 Answers 4

You can test for NaN specifically by using Number.isNaN, which is subtly different from plain isNaN: It only returns true if its argument is a number (whose value is NaN). In other words, it won't try to coerce strings and other values to numbers.

Demo:

const values = [
  12,
  NaN,
  "hello",
  { foo: "bar" },
  NaN,
  null,
  undefined,
  -3.14,
];

const filtered = values.filter(x => !Number.isNaN(x));

console.log(filtered);

Number.isNaN is new in ECMAScript 6. It is supported by every browser except Internet Explorer. In case you need to support IE, here's a simple workaround:

if (!Number.isNaN) {
    Number.isNaN = function (x) { return x !== x; };
}

you can use typeof (to check that's a number) in bination with isNaN

Note that typeof NaN returns "number"

typeof x === "number" && isNaN(x) 

Another solution is to use Number.isNaN which will not trying to convert the parameter into a number. So it will return true only when the parameter is NaN

You should be able to use Number.isNaN

console.log([1, "foo", NaN, "bar"].filter((x) => !Number.isNaN(x)))

I’ve seen this parison check, not sure if you could make it work for you.

var nanValue = NaN;
if(nanValue !== nanValue) // Returns true!
    alert('nanValue is NaN');