Variables and Equality

Scope

There are two types of scope: block scope and module scope. Variables declared in a block can be accessed within that block. Variables cannot be redeclared in a block but can be shadow a declaration from a higher scope. Variables declared at the top level have module scope.

Variable Declaration

Variables can be declared using let or const. Variables declared as const cannot be reassigned.

const VERSION_STRING = '1.0.0' 

Variables can also be declared using 'destructuring declaration'

let point = {x:1, y:2}
let {x,y} = point // x is 1 and y is 2

Equality and Strict Equality

Variables can be tested for equality using the == operator. The == can be used for most situations and strict equality(===) is different in the following ways.

• 1(Int) and 1.0(Float) are not strictly equal
• -0.0 and 0.0 are not strictly equal
• NaN and NaN are strictly equal Strict equality is used by Map.