How to correctly use JavaScript indexOf in a date array

Question

Here is the code:

var collection = [new Date(2014, 11, 25), new Date(2014, 11, 24)];
var d=new Date(2014, 11, 24);

var idx= collection.indexOf(d);

Answer 1

This is because your "d" object is the different object. In other words:

var d = new Date(2014, 11, 24);

d === new Date(2014, 11, 24); // returns false

You can try this:

var d = new Date(2014, 11, 24);
var collection = [new Date(2014, 11, 25), d];

var idx = collection.indexOf(d); // returns 1