String.fromCodePoint()

num1, …, numN

An integer between 0 and 0x10FFFF (inclusive) representing a Unicode code point.

A string created by using the specified sequence of code points.

RangeError

Thrown if numN is not an integer, is less than 0, or is greater than 0x10FFFF after being converted to a number.

Because fromCodePoint() is a static method of String, you always use it as String.fromCodePoint(), rather than as a method of a String value you created.

Unicode code points range from 0 to 1114111 (0x10FFFF). In UTF-16, each string index is a code unit with value 0 – 65535. Higher code points are represented by a pair of 16-bit surrogate pseudo-characters. Therefore, fromCodePoint() may return a string whose length (in UTF-16 code units) is larger than the number of arguments passed. For information on Unicode, see UTF-16 characters, Unicode code points, and grapheme clusters.

Valid input:

String.fromCodePoint(42); // "*"
String.fromCodePoint(65, 90); // "AZ"
String.fromCodePoint(0x404); // "\u0404" === "Є"
String.fromCodePoint(0x2f804); // "\uD87E\uDC04"
String.fromCodePoint(194564); // "\uD87E\uDC04"
String.fromCodePoint(0x1d306, 0x61, 0x1d307); // "\uD834\uDF06a\uD834\uDF07"

Invalid input:

String.fromCodePoint("_"); // RangeError
String.fromCodePoint(Infinity); // RangeError
String.fromCodePoint(-1); // RangeError
String.fromCodePoint(3.14); // RangeError
String.fromCodePoint(3e-2); // RangeError
String.fromCodePoint(NaN); // RangeError

String.fromCharCode() cannot return supplementary characters (i.e. code points 0x010000 – 0x10FFFF) by specifying their code point. Instead, it requires the UTF-16 surrogate pair in order to return a supplementary character:

String.fromCharCode(0xd83c, 0xdf03); // Code Point U+1F303 "Night with
String.fromCharCode(55356, 57091); // Stars" === "\uD83C\uDF03"

String.fromCodePoint(), on the other hand, can return 4-byte supplementary characters, as well as the more common 2-byte BMP characters, by specifying their code point (which is equivalent to the UTF-32 code unit):

String.fromCodePoint(0x1f303); // or 127747 in decimal

• Polyfill of String.fromCodePoint in core-js
• String.fromCharCode()
• String.prototype.charAt()
• String.prototype.codePointAt()
• String.prototype.charCodeAt()