SOURCE

var num = 10;
var obj = {
    num:20
}
obj.fn = (function(num){
    this.num = 3*num;
    num++;
    return function(n){
        this.num+=n;
        num++;
        console.log(num);
    }
})(obj.num)
var fn = obj.fn;
fn(5);
obj.fn(10);
console.log(num,obj.num)