JavaScript: Number.isNaN

By Xah Lee. Date: . Last updated: .

Number.isNaN ( number )

If number is NaN, return true, else false.

(NaN is a primitive value of number type that represents “not a number”.)

〔►see JavaScript: NaN

console.log ( Number.isNaN ( NaN ) ); // true

console.log ( Number.isNaN ( "NaN" ) ); // false
console.log ( Number.isNaN ( "3" ) ); // false
console.log ( Number.isNaN ( 3 ) ); // false
console.log ( Number.isNaN ( Infinity ) ); // false

Number.isNaN and the global isNaN are different.

isNaN converts argument to number first. Number.isNaN does not.

〔►see JavaScript: isNaN

Reference

ECMAScript® 2016 Language Specification#sec-number.isnan

Number Topic


  1. JavaScript: Number Object
  2. JavaScript: Number Constructor
  3. JavaScript: Number.prototype

String Topic

  1. JavaScript: Default Charset/Encoding
  2. JavaScript: String is 16-Bit Unit Sequence
  3. JavaScript: Unicode Character Escape Sequence
  4. JavaScript: Allowed Characters in Identifier
  5. HTML: Allowed Characters in id Attribute
  6. HTML: Character Sets and Encoding
  7. HTML XML Entities

  1. JavaScript: Template String
  2. JavaScript: Convert String to Number
  3. JavaScript Encode URL, Escape String
  4. JavaScript: Format Number
  5. JavaScript: JSON Object

  1. JavaScript: String Object
  2. JavaScript: String.prototype
  3. JavaScript: String Constructor
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