JavaScript Confusions

I finally received my JavaScript book, so this means that I will begin learning JavaScript. That also means that I would start posting my errors here and asking for explanations on things I don't understand. So, instead of creating a ton of topics dedicating to one question, I'm dedicating this thread to all of my questions. Hope that this doesn't get confusing

What is the difference between ECMAScripts and JavaScript? I used to think that ECMAScript was just another name for JavaScript, but the book I'm reading keeps referring to them as two different entities. It keeps talking about JavaScript 1.5 and ECMAScript v3... are they really a separate entity?

Javascript is basically an implementation, or slang, of ECMAScript.

Say you have English, then you have the slang version of English with little quirks that everyone in a neighborhood uses.

Oh, I see... so I'm actually learning a slang version of ECMAScript.

Another 'confusion'. It's about lambda functions this time. I remember that Joebert has once used the term (lambda function), and now that I know how one looks, I don't really know how to use it.


All that does is prints function(x) { return x*x; } on the screen. I'm confused with this thing. It probably doesn't matter this far into the book, I'm just stumped over the lambda functions and I don't see any use whatsoever in it right now.

wikipedia has a pretty good explanation of it:

http://en.wikipedia.org/wiki/Lambda_calculus

I'm sorry, but I just wanted to know how a lambda function could be useful in JavaScript. Thanks for that reply though.

I've got another question...
I've got the following code. I created it myself with a little help of google. It works, but I just have one question.

Why does it have to have the following highlighted lines in it to work properly?
Without those highlighted lines of javascript, the code doesn't write anything in those divs.....

well, I hope I get this right considering I'm still learning javascript myself. Whenever you call a function without the onload event, the function is running before the rest of the page loads. So basically with this function, without the onload event, javascript would look for "#box" before it had been loaded onto the page, javascript wouldn't find the box because it hasn't loaded yet, and therefor wouldn't run the function. the onload event tells javascript to wait until everything is loaded before running the function.

I think that you are right.. the following works without the onload function.

Thanks.

Yes, but the neighborhood in this case is the entire Internet and a handful of desktop applications.

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As for lambda functions, or anonymous functions which is a much easier term to remember them by, it used to be that you would define them attached to a legacy event such as onclick, onmousemove, etc.



However with people, libraries, etc moving to the likes of addEventListener/attachEvent you generally don't use that much anymore.

There is still however, a use for them in array sorting.

And since I hadn't seen those last few posts until I replied,



Looks like you guys have that figured out, I just want to point something out.

When you define something in what seems like a "global" content [context], it's actually going into the "window" context. So in the case of that piece of code you have "onload = ..." is like putting down "window.onload = ..."

Oh, I see... I once tried that using 'document.onload = ..." but that didn't work... I understand why now.

I have another question now.

Before I tell you what the problem is, I want to explain what I want to do. I want to make it so that the text 'This is some text for this program!' would go between box1 and box2. If at first refresh it's at box1 then the second refresh it would be in box2 and then back to box1 and so on. Not random anymore.

What's happening with this code though is that the text stays at the top one and that's it... it doesn't move back and forth with those.

In order to alternate between refreshes, you'll have to use cookies to keep track of what happened on the last page load.

Basically what you'll do is look for your cookie, if it doesn't exist or the value of your cookie is "box1", then you will set the value of the cookie to "box2" and work with box two. Otherwise you will set the cookie to "box1" and work with box one.

Has your book gone on to cookies yet ?

Yeah... it mentioned cookies once or twice... I guess I'll have to read on before I can continue with this. Thanks for the reply. Don't know why I haven't thought about cookies.

I have the following piece of code: I'm just trying to add a number to a number. Instead of adding though, it concatenates.

What's annoying is that I have the following code: And it works perfectly

Any help? Thanks

The following fix my issue: