scope-mindfuck.js

let val = 'global 1'
this.val = 'global 2'

console.log('val = ' + val)

class Foo {
    constructor() {
        this.val = 'property'
    }
}

let foo = new Foo()

foo.method = function() {
    function test() {
        // this is set to the global object
        console.log('test this.val=' + this.val)
        this.val = 'global 3'
    }
    test()
}

foo.method()
this.val = 'global 4'
foo.method()