string.startsWith

str.startsWith(searchString[, position])

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

console.log(str.startsWith('To be')         // true
console.log(str.startsWith('not to be')     // false
console.log(str.startsWith('not to be', 10) // true

if (!String.prototype.startsWith) {
    String.prototype.startsWith = function(searchString, position){
      return this.substr(position || 0, searchString.length) === searchString;
  };
}