JS: String.fromCharCode

String.fromCharCode ( …codeUnits )

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

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.

(you cannot use String.fromCharCode() to create a string that contains a character with Unicode codepoint greater than 65535.)

Note: you should use String.fromCodePoint() instead.

〔►see JS: String.fromCodePoint〕

〔►see JS: String Code Unit vs Code Point〕

// convert sequence of unicode code point to string
let s = String.fromCharCode ( 97, 98);
console.log ( s === "ab" ); // true
// 97 is the code point for letter “a”
// 98 is the code point for letter “b”

// String.fromCharCode won't work as expected if code point is greater than 65535 (that's 2^16 )

let t = String.fromCharCode ( 128514 );

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

console.log ( t ); // prints , WRONG

Reference

ECMAScript 2015 §Text Processing#sec-string.fromcharcode