Javascript is weird when compared to other popular programming languages. If you search it on the Internet, there’re a lot of articles talking about the weirdness of Javascript. For example: and

Here are something make me feel Javascript is a quite special programming language:

let ary = []
ary[(] = 1
ary[1.1] = 1
ary[true] = 1

Lots of other programming languages do not allow non integer indices for array at all

let ary = [0, 1, 2]
ary[0] === ary[[0]] // true
ary[0] === ary[[[0]]] // true

I believe almost all the other languages will just throw errors when using brackets like that.

“Not a Number” is a number, sounds funny, and if to check a value is NaN, built-in function isNaN must be used as == or === always return false. NaN makes Javascript more special.

1 / 0 // Infinity
0 / 0 // NaN

Other languages will probably just throw errors for dividing zero operation

Before class was introduced to Javascript, using constructor pattern to create an object in Javascript is new + function

function Foo() {}
let foo = new Foo()

new keyword + function is special, I don’t think this is common in other programming languages