I’ve done the similar challenge in day 20 before (Hawking’s voice synthesizer), but it’s more challenging (not really).

I am too tired to explain the challange. Perhaps, the only thing that’s worth-explaining is this part:

I’ve read this binding mechanism from This & Prototype of YDKJS (You Don’t Know JavaScript) book series and put it into action here.

Passing empty object (DMZ) to the first parameter of Function.prototype.bind and then passing any values to the rest of parameters is to set default arguments passed to callback and have it ignore the this binding. Consequently, after it was applied, the callback would be bound to empty object that has no link to [[Prototype]] chain and arguments are set without having to invoke the callback, something like callback(arg1, arg2);.

Here’s the demo and my half-assed solution below.