Question

Basically can I do the following…

var obj = {}:
obj.falsey = true;
if(obj){
   //code not executed
}else{
   //code executed
}

I could take advantage of the fact !,+,~…
Call valueOf/toString and do the following, but I would like to avoid that.

var obj = {valueOf:function(){return 0}}:
obj.falsey = true;
if(!!obj){
   //code not executed
}else{
   //code executed
}

Why would I want to do this? Because I’m curious 😀

Answer 1

You can borrow a false Number,Boolean…. from an iframe and extend its prototype.

Basically the following doesn’t work because Numbers are a primitive value.

var x = 0;
x.test = 'yo';
console.log(x.test);

This does, but obviously this pollutes the Number.prototype, so you should really borrow a different Number object from another iframe.

var x = 0;
Number.prototype.test = 'yo';
console.log(x.test);

Ultimately, just not a very good idea.