String.fromCodePoint()

The static String.fromCodePoint() method returns a string created by using the specified sequence of code points.

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Syntax

String.fromCodePoint(num1[, ...[, numN]])

Parameters

num1, ..., numN

A sequence of code points.

Return value

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

Exceptions

• A RangeError is thrown if an invalid Unicode code point is given (e.g. "RangeError: NaN is not a valid code point").

Description

This method returns a string and not a String object.

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

Examples

Using fromCodePoint()

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

Compared to fromCharCode()

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

The String.fromCodePoint method has been added to ECMAScript 2015 and may not be supported in all web browsers or environments yet. Use the code below for a polyfill:

if (!String.fromCodePoint) (function(stringFromCharCode) {
    var fromCodePoint = function(_) {
      var codeUnits = [], codeLen = 0, result = "";
      for (var index=0, len = arguments.length; index !== len; ++index) {
        var codePoint = +arguments[index];
        // correctly handles all cases including `NaN`, `-Infinity`, `+Infinity`
        // The surrounding `!(...)` is required to correctly handle `NaN` cases
        // The (codePoint>>>0) === codePoint clause handles decimals and negatives
        if (!(codePoint < 0x10FFFF && (codePoint>>>0) === codePoint))
          throw RangeError("Invalid code point: " + codePoint);
        if (codePoint <= 0xFFFF) { // BMP code point
          codeLen = codeUnits.push(codePoint);
        } else { // Astral code point; split in surrogate halves
          // https://mathiasbynens.be/notes/javascript-encoding#surrogate-formulae
          codePoint -= 0x10000;
          codeLen = codeUnits.push(
            (codePoint >> 10) + 0xD800,  // highSurrogate
            (codePoint % 0x400) + 0xDC00 // lowSurrogate
          );
        }
        if (codeLen >= 0x3fff) {
          result += stringFromCharCode.apply(null, codeUnits);
          codeUnits.length = 0;
        }
      }
      return result + stringFromCharCode.apply(null, codeUnits);
    };
    try { // IE 8 only supports `Object.defineProperty` on DOM elements
      Object.defineProperty(String, "fromCodePoint", {
        "value": fromCodePoint, "configurable": true, "writable": true
      });
    } catch(e) {
      String.fromCodePoint = fromCodePoint;
    }
}(String.fromCharCode));

Specifications

Browser compatibility

The compatibility table in this page is generated from structured data. If you'd like to contribute to the data, please check out https://github.com/mdn/browser-compat-data and send us a pull request.

See also

• String.fromCharCode()
• String.prototype.charAt()
• String.prototype.codePointAt()
• String.prototype.charCodeAt()