JavaScript Date Object Comparison

Question

When comparing date objects in Javascript I found that even comparing the same date does not return true.

 var startDate1 = new Date("02/10/2012");  var startDate2 = new Date("01/10/2012");  var startDate3 = new Date("01/10/2012");  alert(startDate1>startDate2); // true  alert(startDate2==startDate3); //false 

How could I compare the equality of these dates? I am interested in utilizing the native Date object of JS and not any third party libraries since its not appropriate to use a third party JS just to compare the dates.

Answer 1

That is because in the second case, the actual date objects are compared, and two objects are never equal to each other. Coerce them to number:

 alert( +startDate2 == +startDate3 ); // true 

If you want a more explicity conversion to number, use either:

 alert( startDate2.getTime() == startDate3.getTime() ); // true 

or

 alert( Number(startDate2) == Number(startDate3) ); // true 

Oh, a reference to the spec: §11.9.3 The Abstract Equality Comparison Algorithm which basically says when comparing objects, obj1 == obj2 is true only if they refer to the same object, otherwise the result is false.