String.fromCodePoint()

Baseline Widely available

This feature is well established and works across many devices and browser versions. It’s been available across browsers since September 2015.

Resumen

El método estatico String.fromCodePoint() devuelve una cadena creada por una secuencia de puntos de codigo.

Sintaxis

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

Parametros

num1, ..., numN

Una secuencia de puntos de código.

Throws

RangeError

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

Descripción

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.

Ejemplos

Ejemplos: Usando fromCodePoint()

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

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
js
// String.fromCharCode() alone cannot get the character at such a high code point
// The following, on the other hand, can return a 4-byte character as well as the
// usual 2-byte ones (i.e., it can return a single character which actually has
// a string length of 2 instead of 1!)
console.log(String.fromCodePoint(0x2f804)); // or 194564 in decimal

Polyfill

The String.fromCodePoint method has been added to the ECMAScript standard in version 6 and may not be supported in all web browsers or environments yet. Use the code below for a polyfill:

js
/*! http://mths.be/fromcodepoint v0.1.0 by @mathias */
if (!String.fromCodePoint) {
  (function () {
    var defineProperty = (function () {
      // IE 8 only supports `Object.defineProperty` on DOM elements
      try {
        var object = {};
        var $defineProperty = Object.defineProperty;
        var result = $defineProperty(object, object, object) && $defineProperty;
      } catch (error) {}
      return result;
    })();
    var stringFromCharCode = String.fromCharCode;
    var floor = Math.floor;
    var fromCodePoint = function () {
      var MAX_SIZE = 0x4000;
      var codeUnits = [];
      var highSurrogate;
      var lowSurrogate;
      var index = -1;
      var length = arguments.length;
      if (!length) {
        return "";
      }
      var result = "";
      while (++index < length) {
        var codePoint = Number(arguments[index]);
        if (
          !isFinite(codePoint) || // `NaN`, `+Infinity`, or `-Infinity`
          codePoint < 0 || // not a valid Unicode code point
          codePoint > 0x10ffff || // not a valid Unicode code point
          floor(codePoint) != codePoint // not an integer
        ) {
          throw RangeError("Invalid code point: " + codePoint);
        }
        if (codePoint <= 0xffff) {
          // BMP code point
          codeUnits.push(codePoint);
        } else {
          // Astral code point; split in surrogate halves
          // http://mathiasbynens.be/notes/javascript-encoding#surrogate-formulae
          codePoint -= 0x10000;
          highSurrogate = (codePoint >> 10) + 0xd800;
          lowSurrogate = (codePoint % 0x400) + 0xdc00;
          codeUnits.push(highSurrogate, lowSurrogate);
        }
        if (index + 1 == length || codeUnits.length > MAX_SIZE) {
          result += stringFromCharCode.apply(null, codeUnits);
          codeUnits.length = 0;
        }
      }
      return result;
    };
    if (defineProperty) {
      defineProperty(String, "fromCodePoint", {
        value: fromCodePoint,
        configurable: true,
        writable: true,
      });
    } else {
      String.fromCodePoint = fromCodePoint;
    }
  })();
}

Especificaciones

Specification
ECMAScript Language Specification
# sec-string.fromcodepoint

Compatibilidad con navegadores

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See also