Empty array is truthy or not in JavaScript? [duplicate]

Question

I'm a bit confused by the following results, could someone kindly point out what happened under the hood? why Boolean([]) will return true? and loosely compare empty array to a Boolean [] == false would evaluate to true?
but strict comparison would evaluate to false??

This is the part I don't get it

Thanks so much!

Boolean([])
//true

[] == false
//true

[] === false
//false

Empty array in javascript is truthy inorder to check for array you have to check the length of array if ([].length) {// do something } else {// do something else} — Ashish Choubey
– Ashish Choubey, Commented Jul 1, 2020 at 3:58

Edric · Accepted Answer · 2020-07-01 04:31:27Z

10

The easiest way to check reliably is to use the length property.

[].length // 0, falsy

['something'].length // 1. truthy

See the official spec for more info.

edited Jul 1, 2020 at 4:31

Edric

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answered Jul 1, 2020 at 3:56

Goofballtech

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2 Comments

Code_Like_a_Newbie Over a year ago

but why Boolean([]) will return true? and loosely compare empty array to a Boolean [] == false would evaluate to true? but strict comparison would evaluate to false?? This is the part I don't get it

Goofballtech Over a year ago

Its not all logical. See the above linked repo. There are many example of these things that are just crazy. It's goof to know they are there when looking for a weird error though.

Siva Kondapi Venkata · Accepted Answer · 2020-07-01 10:22:05Z

4

Boolean([]) // => true

Here, [] (Array is object type) is converting to boolean. Since [] has the reference value, after conversion is is true.

.

[] == false // => false

Here, Equality operator loosely check values. Since both sides are different types (object and boolean) and one of side is boolean, So it will covert to (0 or 1) and compare to other side. It will be equivalent to +[] == +false, which will be 0 == 0, will be true

Check MDN document for more details

[] === false // => false

Here, Strict Equality operator. Will check for Type and value Since both are different types, it will be false.

edited Jul 1, 2020 at 10:22

answered Jul 1, 2020 at 6:28

Siva Kondapi Venkata

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2 Comments

Code_Like_a_Newbie Over a year ago

THANKS! Concise explanation

atul mishra Over a year ago

@siva Please correct [] == false // => false.. you added it not false its true some typo

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