JavaScript endsWith function not working

Question

I have a web application. In one of the pages, I go all over the HTML element IDs wether one of them ends with a specified string or not. Every JS functions work on the page but "endsWith" function doesn't work. I really didn't understand the matter. Can anyone help?

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

The above simple JS code doesn't work at all?

Answer 1

As said in this post http://rickyrosario.com/blog/javascript-startswith-and-endswith-implementation-for-strings/

var str = "To be, or not to be, that is the question.";
function strEndsWith(str, suffix) {
    return str.match(suffix+"$")==suffix;
}
alert(strEndsWith(str,"question."));

this will return true if it ends with provided suffix.

JSFIDDLE

EDIT

There is a similar question asked before check it here

the answer says

var str = "To be, or not to be, that is the question$";
String.prototype.endsWith = function(suffix) {
    return this.indexOf(suffix, this.length - suffix.length) !== -1;
};
alert(str.endsWith("$"));

Answer 2

ES5 has no endsWith function (or, for that matter, startsWith). You can roll your own, like this version from MDN:

if (!String.prototype.endsWith) {
    Object.defineProperty(String.prototype, 'endsWith', {
        enumerable: false,
        configurable: false,
        writable: false,
        value: function (searchString, position) {
            position = position || this.length;
            position = position - searchString.length;
            var lastIndex = this.lastIndexOf(searchString);
            return lastIndex !== -1 && lastIndex === position;
        }
    });
}