SOURCE

function foo(x, y) {
    return this.a + x + y
}

function log(value) {
    console.log(value)
}

function test() {
    log(this.a)
    this.fn = foo.bind(null, 1, 2)
    log(this.fn())
}

var a = 100

var b = {a: 105, foo, test}

test.call(b)