String.prototype.codePointAt()

Baseline Widely available

This feature is well established and works across many devices and browser versions. It’s been available across browsers since septiembre de 2015.

El método codePointAt() devuelve un entero no negativo que equivale al valor Unicode code point del carácter.

Sintaxis

str.codePointAt(indice)

Parámetros

indice

Índice del carácter en la cadena del que se quiere obtener el valor del Unicode code point.

Valor de retorno

Un número que equivale al valor code point del carácter especificado en el índice de la cadena; devuelve undefined si no se encuentra carácter en la posición especifica.

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()

js
"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.

js
/*! 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;
    }
  })();
}