Why is [] !== [] in JavaScript?

javascript equality equality-operator
fahrradflucht picture fahrradflucht · Oct 28, 2016 · Viewed 10.4k times · Source

Why is [] !== [] in JavaScript?

I read through https://developer.mozilla.org/en-US/docs/Web/JavaScript/Equality_comparisons_and_sameness but I could not find anything that explains this.

Edit: I don't think this question or this question is an exact duplicate of mine. It asks about the == operator which just behaves crazy. The answer is an answer to my question but it's not the same question.

Answer

Lew picture Lew · Oct 28, 2016

That does a reference check on the two array literals to see if they are the same instance. The fact that you have two literals means that you are constructing two separate arrays, therefore the reference check returns false. This would return true:

var a = []
var b = a

//b === a

This is because we have two references to the same array.

Related questions

Which equals operator (== vs ===) should be used in JavaScript comparisons?

I'm using JSLint to go through JavaScript, and it's returning many suggestions to replace == (two equals signs) with === (three equals signs) when doing things like comparing idSele_UNVEHtype.value.length == 0 inside of an if statement. Is there a performance benefit …

Read More
JavaScript - === vs == operators performance

A few weeks ago, I have read this thread Is < faster than <=? about comparison operators in C. It was said that there is no difference in the performance between < and <= as they are interpreted as same/…

Read More
Checking if two Dates have the same date info

How can I check if two different date objects have the same date information(having same day, month, year ...)? I have tried "==", "===" and .equals but none seems to work.

Read More