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The codePointAt()
method returns a non-negative integer that is the Unicode code point value.
Syntax
str.codePointAt(pos)
Parameters
pos
- Position of an element in the String to return the code point value from.
Return value
A number representing the code unit value of the character at the given index; undefined
if there is no element at pos
.
Description
If there is no element at the specified position, undefined
is returned. If no UTF-16 surrogate pair begins at pos
, the code unit at pos
is returned.
Examples
Using codePointAt()
'ABC'.codePointAt(1); // 66 '\uD800\uDC00'.codePointAt(0); // 65536 'XYZ'.codePointAt(42); // undefined
Polyfill
The following extends Strings to include the codePointAt()
function as specified in ECMAScript 6 for browsers not supporting it natively.
/*! https://mths.be/codepointat v0.1.0 by @mathias */ if (!String.prototype.codePointAt) { (function() { 'use strict'; // needed to support `apply`/`call` with `undefined`/`null` var codePointAt = function(position) { if (this == null) { throw TypeError(); } var string = String(this); var size = string.length; // `ToInteger` var index = position ? Number(position) : 0; if (index != index) { // better `isNaN` index = 0; } // Account for out-of-bounds indices: if (index < 0 || index >= size) { return undefined; } // Get the first code unit var first = string.charCodeAt(index); var second; if ( // check if it’s the start of a surrogate pair first >= 0xD800 && first <= 0xDBFF && // high surrogate size > index + 1 // there is a next code unit ) { second = string.charCodeAt(index + 1); if (second >= 0xDC00 && second <= 0xDFFF) { // low surrogate // https://mathiasbynens.be/notes/javascript-encoding#surrogate-formulae return (first - 0xD800) * 0x400 + second - 0xDC00 + 0x10000; } } return first; }; if (Object.defineProperty) { Object.defineProperty(String.prototype, 'codePointAt', { 'value': codePointAt, 'configurable': true, 'writable': true }); } else { String.prototype.codePointAt = codePointAt; } }()); }
Specifications
Specification | Status | Comment |
---|---|---|
ECMAScript 2015 (6th Edition, ECMA-262) The definition of 'String.prototype.codePointAt' in that specification. |
Standard | Initial definition. |
ECMAScript 2017 Draft (ECMA-262) The definition of 'String.prototype.codePointAt' in that specification. |
Draft |
Browser compatibility
Feature | Chrome | Firefox (Gecko) | Internet Explorer | Opera | Safari |
---|---|---|---|---|---|
Basic support | 41 | 29 (29) | 11 | 28 | No support |
Feature | Android | Chrome for Android | Firefox Mobile (Gecko) | IE Mobile | Opera Mobile | Safari Mobile |
---|---|---|---|---|---|---|
Basic support | No support | No support | 29.0 (29) | No support | No support | No support |
See also
Štítky a přispěvatelé do dokumentace
Štítky:
Přispěvatelé této stránky:
eduardoboucas,
metamatt,
fscholz,
fasttime,
ziyunfei,
Mingun,
trueorfalse
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