The lesson is, always look for a method that does what you want.
Whether one can avoid it or not is a different argument, as obviously there aren't that many choices on the browser, but I often argue it is a broken behavior, it annoys me every time I have to use Javascript.
The real mistake was making [] equal zero.
So a simple fraction type can be done like this:
function Fraction(n, d) {
this.n = n;
this.d = d;
}
Fraction.prototype.toString = function() {
return this.n / this.d;
};
//Demo
var x = new Fraction(1, 2);
alert(x * 38); //19
alert(x + x); //1[].length is what you want for the second. IIRC [] isn't false in Python either.
>>> if (): print "tuple"
>>> if []: print "list"
>>> if {}: print "dict"
>>> if set(): print "set"
>>> if "": print "string"
>>> import collections
>>> if collections.Counter(): print "counter"
>>> if collections.deque(): print "deque"
>>>