I like your post, because in the beginning you used if (var) and in the end you used if (var != null). What's the big difference?
On 8 fév, 20:20, Jan Kassens <[email protected]> wrote: > The ReferenceError will only be thrown if the variable is not defined, > not if the value of the variable is undefined. Let me illustrate: > > Example one (given there are no variables defined elsewhere): > if (nowhereDefinedVar) ... // throws an error > > Example two: > var someUnintializedVar; // var is now defined and has the initial > value of undefined > // later > if (someUninitialized != null) alert("yay, the variable has a value"); > else alert("the var is either null or undefined"); > > If you want to check, whether another included script has defined some > global variable you should indeed use: > if (window.someVariableMaybeDefinedElsewhere != null) ... > > > > On Tue, Feb 8, 2011 at 8:07 PM, Savageman <[email protected]> wrote: > > I agree with what you say: putting the static methods (which doesn't > > modify the object) are in the namespace than the prototype. > > > I just made some tests and "discovered" (noticed would be better) than > > the Object behaves a bit differently. They get something in addition > > to the other native types, and the prototype is searched when trying > > to access a non-existent property.http://jsfiddle.net/8DG63/4/ > > This doesn't work with other native types (Number, String, etc.) and > > accessing a non-existent property doesn't search through the native's > > prototype to fetch the it. > > > My next question (which is more an observation I can't really explain) > > is about accessing non-existent properties. Reading the typeOf() > > function, I have been reading (item.$family) and this popped in my > > mind: > > - What if the $family property doesn't exists, that can happen, right? > > I've always been screwed by this ReferenceError Exception: "undefined > > variable <name here>". > > > So I did some tests and observed that no exception is thrown when > > accessing an undefined property. I find this quite inconsistent, but > > that's the language and how it works... > > The real question is: can I solve this annoying thing by checking > > window.myUndefinedVar (or window['myUndefinedVar']) instead of the var > > directly to get rid of this? I'm not wanting to silently avoid this > > undefined exception thing, it could just simplify a lot something like > > this: > > > if (typeof(myVar) != 'undefined' && myVar != null) could be simplified > > as: if (window.myVar != null). Is it safe? > > > On 8 fév, 13:44, Christoph Pojer <[email protected]> wrote: > >> Those methods are static methods on the native types. Methods on the > >> prototype modify the object they are called from, static methods just act > >> on > >> the passed arguments. > > >> In the same way, ' abc '.trim() is a dynamic method while Object.each(obj, > >> fn) is static.
