CODEWITHSUNDEEP
javascript
scusyxx
scusyxx

Reputation: 1244

Javascript equality

I have been trying to understand Javascript equality. Can you please tell me why the following line returns false?

alert((function a(){}) == (function a(){})) // false

But as you can see from the following cases < returns false but <= returns true, which means == should return true but it is false. Do you have any idea, WHY?

alert((function a(){}) < (function a(){})) // false
alert((function a(){}) > (function a(){})) // false
alert((function a(){}) <= (function a(){})) // true
alert((function a(){}) >= (function a(){})) // true

Upvotes: 3

Views: 605

Answers (3)

Wulfram
Wulfram

Reputation: 3382

A little known fact is that Javascript equality operator is actually === not ==. When you run a comparison operator on a function, you are comparing the value of the reference (the location in memory) not the function itself. Since the functions are all separate objects, == will not return true.

From "Javascript - The Definitive Guide" http://docstore.mik.ua/orelly/webprog/jscript/ch05_04.htm

On the other hand, objects, arrays, and functions are compared by reference. This means that two variables are equal only if they refer to the same object.

Upvotes: 1

jpniederer
jpniederer

Reputation: 140

If we test that the functions are not equal, we get true.

alert((function a(){}) != (function a(){})) //true

This is because each of the functions are a different object and why the equality check returns false.

Upvotes: 0

xdazz
xdazz

Reputation: 160833

You are comparing two object using < , <=, and they are actually compared with string they could covert to.

"function a(){}" < "function a(){}" is false.

"function a(){}" <= "function a(){}" is true.

EDIT: Why (function a(){}) == (function a(){}) returns false is because you are compare same type with ==, so they don't need to covert to string or number to compare, they are two different objects.

Upvotes: 5

Related Questions