exploring javascript type auto-coercion (and its pitfalls)

gistfile1.txt

// **********
// NOTE: this is a stupid trivial example illustrating automatic
// type-coercion, not an example of the kind of data-structure logic
// you'd ever actually use. don't miss the forest for the trees.
// Read down in the comment thread for 'myCoolString' for a slightly
// more sensible example.
//
// NOTE #2: this gist thread was spawned from a twitter discussion
// about `parseInt(0/1,19)==18`:
// https://twitter.com/getify/status/221009838006747136
// **********


var myObj = {
   _val: [10,5,7,9,-1,4,13,6],
   toString: function(){
     return ""+Math.max.apply(this,this._val);
   }
};

parseInt(myObj); // 13 ==> this is part of what makes javascript awesome

I have no "respect" for any language. I'm not even sure what that means. Technology decisions are tradeoffs. The choice of one language over another is a matter of choosing the best tool for the job at hand. I absolutely respect the toolmakers, but the tools are just tools. If you point out a flaw with my tool, I may argue that said flaw is a feature, but neither my tool nor I shall feel disrespected.

I guess that parseInt(1/0,19)==18 is just my own personal semantic WTF. I'm sure if you're experienced enough with JavaScript, you can look at a function that (a) purports to produce integers that match its parameters, (b) accepts Infinity as one of the parameters, and (c) produces the number 18, and use it as an example of the greatness of JavaScript.

Many of us continue to shake our heads, and struggle to understand. Perhaps one day we will become enlightened. Then shall we understand parseInt(1/0,19)==18. Until then, we trudge along in the darkness of our stupidity.

@bhudgeons
parseInt(1/0,19)==18 is clearly a semantic WTF... for pretty much everyone, myself included. There's never been an argument about that.

There are plenty of other semantic WTFs too. My personal "favorite" is typeof NaN == "number".

The question has been, is the language "flawed" by allowing that (or rather, not ensuring some yet-to-be-well-defined alternative)? And more importantly, if we were to consider changing the language to "fix" the "flaw", would we REALLY be better off, or is that just a "grass is always greener" conundrum?

I've been trying to illustrate that all the alternatives are worse. You're not in the "darkness of stupidity" because you disagree. You just value different things from the language than I do.

:)

I woud use valueOf here instead of toString.