JSFuckery

Jan 7 · lroellin

isNaN(NaN) // true
typeof(NaN) // 'number'

var scopes to function

Jan 7 · lroellin

function foo() {
    {
        var x = 5
        let y = 6
        const z = 7
    }
    console.log(x)
    console.log(y)
    console.log(z)
}
foo() // 5, undefined, undefined

Automatic Global Scope

Jan 7 · lroellin

Variables without any qualifier (var, let/const) are automatically in the global scope (after executing the block)

console.log(x) // x is not defined
function foo() {
    x = 5
}
// x is still not defined
foo()
console.log(x) // 5