Javascript Incompatibilities/Inconsistencies [closed]

Answer 1

var x = new Boolean(false); if (x) ... else...;

Is the 'if' or 'else' branch taken?

var x = "hi", y = new String("hi");

what is the typeof(x) and typeof(y) ?

Edit:..

parseInt("017") produces 15 (octal) instead of 17

The 'Error' object is a different signature from IE to Firefox.

When using objects as hashmap's, you need to use object.hasOwnProperty(key) to ensure that the property is not inherited through the prototype chain.

Answer 2

Well, there's a problem with implied semicolons.

return {
    a: 1,
    b: 2
}

Some people like opening brackets on its own line, like this:

return
{
    a: 1,
    b: 2
}

However, this last statement will return undefined, since the parser sees:

return;
{
    a: 1,
    b: 2
}

Answer 3

Another one (don't think this comes up very often):

(typeof document.getElementById)

in IE: "object"

in Firefox: "function"

Answer 4

Yet another one:

Regular expressions from Firefox to IE, there are lots of inconsistencies:

For the description: http://blog.stevenlevithan.com/archives/cross-browser-split

He publishes a fixed version of the RegEx object, and a testing page: http://stevenlevithan.com/demo/split.cfm

Answer 5

An extension to altCognito's point.. Element isn't a defined base type either...

//uses jQuery
function getSomething(input) {
   if (typeof(input) == string)
       input = $(input)[0] || $('#'+input)[0] || null;

   if (input instanceof Element)
       input = $(input);

   if (input instanceOf jQuery) {
       ...do something...
   }
}

I had to replace the instanceOf Element with..

if (input && input.tagName)...

Would be nice if DOM elements were properly base classed in IE all around.

Answer 6

There are almost no inconsistencies in JavaScript implementations across browsers. If there were, it would be a nightmare multiplied (by the multiple inconsistencies in DOM implementation). So "Top Ten Javascript Incompatibilities/Inconsistencies" can probably only be populated with "Bottom One" you spotted. Indeed there could be a pair more, but I would hardly expect them to be major or even worth attention.