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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 point 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 2015 for browsers not supporting it natively.

/*! http://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
          // 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 {
      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 Latest Draft (ECMA-262)
The definition of 'String.prototype.codePointAt' in that specification.
Living Standard  

Browser compatibility

FeatureChromeEdgeFirefoxInternet ExplorerOperaSafari
Basic support41 Yes29 No2810
FeatureAndroid webviewChrome for AndroidEdge mobileFirefox for AndroidIE mobileOpera AndroidiOS Safari
Basic support Yes Yes Yes29 No Yes10

See also

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 최종 변경: ThomasEugeneBishop,