string.endsWith

str.endsWith(searchString[, length])

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

console.log(str.endsWith('question.')); // true
console.log(str.endsWith('to be'));     // false
console.log(str.endsWith('to be', 19)); // true

if (!String.prototype.endsWith)
  String.prototype.endsWith = function(searchStr, Position) {
      // This works much better than >= because
      // it compensates for NaN:
      if (!(Position < this.length))
        Position = this.length;
      else
        Position |= 0; // round position
      return this.substr(Position - searchStr.length,
                         searchStr.length) === searchStr;
  };