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123

JavaScript Date Object Comparison

rated 0 times [ 128] [ 5] / answers: 1 / hits: 91910 / 13 Years ago, fri, september 30, 2011, 12:00:00

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.

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marib

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1 Year ago

answered 13 Years ago malkajillc · Accepted Answer

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.