The codePointAt()
method returns a non-negative integer that is the UTF-16 encoded code point value.
str.codePointAt(pos)
pos
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.
codePointAt()
'ABC'.codePointAt(1); // 66 '\uD800\uDC00'.codePointAt(0); // 65536 'XYZ'.codePointAt(42); // undefined
The following extends Strings to include the codePointAt()
function as specified in ECMAScript 6 for browsers not supporting it natively.
/*! http://mths.be/codepointat v0.1.0 by @mathias */ if (!str.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 // http://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 { str.codePointAt = codePointAt; } }()); }
Created by Mozilla Contributors, license: CC-BY-SA 2.5