String.prototype.endsWith()

Summary

endsWith()方法用来判断当前字符串是否是以另外一个给定的子字符串“结尾”的，根据判断结果返回 true 或 false。

Syntax

str.endsWith(searchString [, position]);

参数

searchString

要搜索的子字符串。

position

在 str 中搜索 searchString 的结束位置，默认值为 str.length，也就是真正的字符串结尾处。

示例

var str = "To be, or not to be, that is the question.";

alert( str.endsWith("question.") );  // true
alert( str.endsWith("to be") );      // false
alert( str.endsWith("to be", 19) );  // true
alert( str.endsWith("To be", 5) );   // true

Polyfill

/*! https://mths.be/endswith v0.2.0 by @mathias */
if (!String.prototype.endsWith) {
  (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 toString = {}.toString;
    var endsWith = function(search) {
      if (this == null) {
        throw TypeError();
      }
      var string = String(this);
      if (search && toString.call(search) == '[object RegExp]') {
        throw TypeError();
      }
      var stringLength = string.length;
      var searchString = String(search);
      var searchLength = searchString.length;
      var pos = stringLength;
      if (arguments.length > 1) {
        var position = arguments[1];
        if (position !== undefined) {
          // `ToInteger`
          pos = position ? Number(position) : 0;
          if (pos != pos) { // better `isNaN`
            pos = 0;
          }
        }
      }
      var end = Math.min(Math.max(pos, 0), stringLength);
      var start = end - searchLength;
      if (start < 0) {
        return false;
      }
      var index = -1;
      while (++index < searchLength) {
        if (string.charCodeAt(start + index) != searchString.charCodeAt(index)) {
          return false;
        }
      }
      return true;
    };
    if (defineProperty) {
      defineProperty(String.prototype, 'endsWith', {
        'value': endsWith,
        'configurable': true,
        'writable': true
      });
    } else {
      String.prototype.endsWith = endsWith;
    }
  }());
}

规范

浏览器兼容性

相关链接

• String.prototype.startsWith()
• String.prototype.contains()
• String.prototype.indexOf()