Question

What are some of the most detrimental Javascript tricks? Pleas include the “issue seen” and “avoid by” blocks.

Examples:

1. Adding properties to Object.prototype.prop = 1
   Issue seen: for(var i in obj){ alert(i);}
   Avoid by: using hasOwnProperty
   example:
   for(var in in obj)if(obj.hasOwnProperty(i)){alert(i);}

2. Override Number.prototype.valueOf = function(){return Math.random()}
   Issue seen: 4*3 (Depends on Javascript engine)
   Avoid by: delete Number.prototype.valueof (again depends on Javascript engine)

Please include potential solutions if you can’t think of a way to “avoid” the code.

Answer 1

Just read Crock’s appendix, “JavaScript, the bad parts”