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This is an experimental technology, part of the ECMAScript 6 (Harmony) proposal.
Because this technology's specification has not stabilized, check the compatibility table for usage in various browsers. Also note that the syntax and behavior of an experimental technology is subject to change in future version of browsers as the spec changes.
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()
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
// 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:
/*! https://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 // https://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; } }()); }
Specifications
Specification | Status | Comment |
---|---|---|
ECMAScript 6 (ECMA-262) The definition of 'String.fromCodePoint' in that specification. |
Release Candidate | Initial definition. |
Browser compatibility
Feature | Chrome | Firefox (Gecko) | Internet Explorer | Opera | Safari |
---|---|---|---|---|---|
Basic support | 41 | 29 (29) | Not supported | Not supported | Not supported |
Feature | Android | Chrome for Android | Firefox Mobile (Gecko) | IE Mobile | Opera Mobile | Safari Mobile |
---|---|---|---|---|---|---|
Basic support | Not supported | Not supported | 29.0 (29) | Not supported | Not supported | Not supported |