es6.string.ends-with.js 855 Bytes
// 21.1.3.6 String.prototype.endsWith(searchString [, endPosition])
'use strict';
var $export   = require('./$.export')
  , toLength  = require('./$.to-length')
  , context   = require('./$.string-context')
  , ENDS_WITH = 'endsWith'
  , $endsWith = ''[ENDS_WITH];

$export($export.P + $export.F * require('./$.fails-is-regexp')(ENDS_WITH), 'String', {
  endsWith: function endsWith(searchString /*, endPosition = @length */){
    var that = context(this, searchString, ENDS_WITH)
      , $$   = arguments
      , endPosition = $$.length > 1 ? $$[1] : undefined
      , len    = toLength(that.length)
      , end    = endPosition === undefined ? len : Math.min(toLength(endPosition), len)
      , search = String(searchString);
    return $endsWith
      ? $endsWith.call(that, search, end)
      : that.slice(end - search.length, end) === search;
  }
});