CODEWITHSUNDEEP
javascriptperformancedate
Sivaprasad derangula
Sivaprasad derangula

Reputation: 1169

Why Date comparison is showing weird behavior in javascript?

When I'm working with date comparison in javascript, in the browser console I did perform the following operations.

new Date() >= new Date() returned true

new Date() <= new Date() returned true

this looked good as I thought both are equal, if I was correct then

new Date() == new Date() should returns true

Interestingly it returned false. Then I performed below operations as well

new Date() > new Date() returned false

new Date() < new Date() returned false

new Date() != new Date() returns true

which was also fine with my assumption.

If both the new Date() s were returning same time then == should return true along with the >= and <=, other wise either of > or < should return ture as != returning true.

Following table consists expected results and actual results for different cases.

enter image description here

Why is the ACTUAL results column not following any of its preceding columns?

Upvotes: 2

Views: 719

Answers (2)

rodrigocfd
rodrigocfd

Reputation: 8033

Check for equality like you're doing compares the references to the objects. To compare the actual values of the objects themselves, the most common practice is to call getTime() method, which will return the number of milliseconds since 1970-01-01 00:00:00 UTC.

Therefore, the following code will return true:

(new Date()).getTime() == (new Date()).getTime()

Upvotes: 3

Emil S. J&#248;rgensen
Emil S. J&#248;rgensen

Reputation: 6366

Use Date.getTime to compare the timestamp, otherwise you are simply comparing the objects, which we know aren't the same.

var d1 = new Date(),
  d2 = new Date();

function fullCompare(a, b) {
  console.log(a == b, a <= b, a >= b, a < b, a > b);
}
fullCompare(d1, d2);
fullCompare(d1.getTime(), d2.getTime());

Upvotes: 4

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