String.prototype.codePointAt()

The codePointAt() method returns a non-negative integer that is the Unicode code point value at the given position.

Syntax

codePointAt(pos)

Parameters

pos

Position of an element in str to return the code point value from.

Return value

A decimal number representing the code point value of the character at the given pos.

  • If there is no element at pos, returns undefined.
  • If the element at pos is a UTF-16 high surrogate, returns the code point of the surrogate pair.
  • If the element at pos is a UTF-16 low surrogate, returns only the low surrogate code point.

Examples

Using codePointAt()

'ABC'.codePointAt(0)                        // 65
'ABC'.codePointAt(0).toString(16)           // 41

'😍'.codePointAt(0)                         // 128525
'\ud83d\ude0d'.codePointAt(0)               // 128525
'\ud83d\ude0d'.codePointAt(0).toString(16)  // 1f60d

'😍'.codePointAt(1)                         // 56845
'\ud83d\ude0d'.codePointAt(1)               // 56845
'\ud83d\ude0d'.codePointAt(1).toString(16)  // de0d

'ABC'.codePointAt(42)                       // undefined

Looping with codePointAt()

Because indexing to a pos whose element is a UTF-16 low surrogate, returns only the low surrogate, it's better not to index directly into a UTF-16 string.

Instead, use a for...of statement or an Array's forEach() method (or anything which correctly iterates UTF-16 surrogates) to iterate the string, using codePointAt(0) to get the code point of each element. 

for (let codePoint of '\ud83d\udc0e\ud83d\udc71\u2764') {
   console.log(codePoint.codePointAt(0).toString(16))
}
// '1f40e', '1f471', '2764'

Polyfill

The following extends Strings to include the codePointAt() function as specified in ECMAScript 2015 for browsers without native support. 

/*! https://mths.be/codepointat v0.2.0 by @mathias */
if (!String.prototype.codePointAt) {
  (function() {
    'use strict'; // needed to support `apply`/`call` with `undefined`/`null`
    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 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 (defineProperty) {
      defineProperty(String.prototype, 'codePointAt', {
        'value': codePointAt,
        'configurable': true,
        'writable': true
      });
    } else {
      String.prototype.codePointAt = codePointAt;
    }
  }());
}

Specifications

Specification
ECMAScript Language Specification
# sec-string.prototype.codepointat

Browser compatibility

BCD tables only load in the browser

See also