JS: String.fromCharCode

By Xah Lee. Date: . Last updated: .

String.fromCharCode ( …codeUnits )

Return a string, where each character in string has corresponding codeUnits.

[see JS: Character, Code Unit, Code Point]

Each of codeUnit should be a integer from 0 to 65535 inclusive. (Note: 65535 = 2^16 -1). If it is greater than 65535, a value of modulo(codeUnit, 2^16) is used.

(it's possible to use String.fromCharCode() to create a string that contains a character with Unicode codepoint greater than 65535. You have to find the pair of 16 bits values (called surrogate pairs) to form 1 such character.)

Note: most of the time, you probably want String.fromCodePoint() instead.

[see JS: String.fromCodePoint]

// convert sequence of unicode codepoint to string

console.log (
    String.fromCharCode ( 97, 98) === "ab"
); // true

// 97 is the codepoint for letter “a”
// 98 is the codepoint for letter “b”
// String.fromCharCode won't work as expected if codepoint is greater than 65535 (that's 2^16 )

const tt = String.fromCharCode ( 128514 );

// 😂
// name: FACE WITH TEARS OF JOY
// codepoint decimal: 128514
// codepoint hexadecimal: 1f602

console.log ( tt ); // prints , WRONG

Reference

ECMAScript 2015 §Text Processing#sec-string.fromcharcode

Character Topic

  1. JS: Character, Code Unit, Code Point
  2. JS: Convert Character To/From Codepoint
  3. JS: String.fromCodePoint
  4. JS: String.fromCharCode
  5. JS: String.prototype.charAt
  6. JS: String.prototype.charCodeAt
  7. JS: String.prototype.codePointAt
  8. JS: Convert Decimal/Hexadecimal
  9. JS: Unicode Escape Sequence

JS String

  1. String Overview
  2. Template String
  3. Char, Code Unit, Code Point
  4. String Escape Sequence
  5. Unicode Escape Sequence
  6. String to Number
  7. Encode URL, Escape String
  8. Format Number
  9. Source Code Encoding
  10. Allowed Characters in Identifier
  11. String Object
  12. String.prototype
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