JavaScript - Javascript Help...i Don't Understand This

I'm sorry if this is asking too much I just find it much easier to learn interacting directly with experience coders but I'm tryign to understand functions better and wanna make sure I got it right.

the function syntax looks like this right
Code:

function functionname()
{
function code
}

the perameters kinda confuses me, inside them can go variables right? but where do you declare those variables? before the function or in the function?

is it like this?
Code:

function functionname(x)
{
var x="Hello"
}

if thats right do you write the code you want to execute below the variables?
like under var x I wanna make a alert
I would write alert("x")

I'm totally new when it comes to JavaScript and I'm trying to learn new things. Here I found the codes I tried it and it works but I would like to have comments for the code to understand how they have proceeded.
can someone help me and explain these codes with comments?
I really appreciate it.

Code:

var config = {
    "tags": "vfx+compositing",
    "user": "andreasl",
    "scriptTagTarget": "scriptTagDiv",
    "deliciousTarget": "deliciousLinks",
    "callbackFunction": "fetchDelicious"
};

window.onload = function() {
    var url = 'http://feeds.delicious.com/v2/json/' + config.user + '/' + config.tags + '?callback=' + config.callbackFunction;
    var scriptDiv = document.getElementById(config.scriptTagTarget);
    addScriptTag(url, scriptDiv);
};



function addScriptTag(url, scriptDiv) {

    if (scriptDiv.hasChildNodes())
    {
        scriptDiv.removeChild(scriptDiv.firstChild)
    };

    var scriptElement = document.createElement('script');
    scriptElement.setAttribute('src', url);
    scriptDiv.appendChild(scriptElement);
}


function fetchDelicious(json) {
	var html = "";
	for (var i = 0; i < json.length; i++) {
		var uri = json[i].u;
		var description = json[i].d;
		var tags = json[i].t; //array
		var time = json[i].dt; 
		//var n = json[i].n; //new?
		var author = json[i].a;
		var bHtml = "<li><a href=\":u\">:d</a>:t</li>".replace(":u", uri).replace(":d", description); 
		var tagHtml = ""; 
		for(var n = 0; n < tags.length; n++)  { 
		tagHtml += "<li><a href=\"http://delicious.com/:u\">:d</a></li>".replace(":u", [author,tags[n]].join("/")).replace(":d", tags[n]); 
		}
		tagHtml = "<ul>" + tagHtml + "</ul>";
		html += bHtml.replace(":t", tagHtml); 
	}
	html = "<ul>" + html + "</ul>"; 
	document.getElementById(config.deliciousTarget).innerHTML = html;
   

}

I have seen this code-piece different places - to use to make a webpage redirect if it is a mobilephone.
I don't quit understand the code - especially the line:
if (redirectagent.indexOf(redirect_devices[i]) != -1)

- why -1 ? Please help me - I would be so thankful.

Code:

<script language=javascript>
var redirectagent = navigator.userAgent.toLowerCase();
var redirect_devices = ['vnd.wap.xhtml+xml', 'sony', 'symbian', 'nokia', 'samsung', 'mobile', 'windows ce', 'epoc', 'nitro', 'j2me', 'midp-', 'cldc-', 'netfront', 'mot', 'up.browser', 'up.link', 'audiovox', 'blackberry', 'ericsson', 'panasonic', 'philips', 'sanyo', 'sharp', 'sie-', 'portalmmm', 'blazer', 'avantgo', 'danger', 'palm', 'series60', 'palmsource',  'smartphone', 'rover', 'au-mic', 'alcatel', 'ericy', 'vodafone', 'wap1', 'wap2', 'teleca',, 'lge', 'lg-', 'iphone', 'android', 'htc', 'dream', 'webos', 'bolt', ];
for (var i in redirect_devices) {
if (redirectagent.indexOf(redirect_devices[i]) != -1) {
location.replace("http://www.example.com");
	}
}
</script>

i wrote like this:
Code:

var a = function b(){
	return b;
};
alert(a() === a );

and ie6~ie8 return false , ie9 chrome ff return true.
how to explain it?

and
Code:

var a = function b(){
};
alert( typeof b );

b is undefined in most of browser but is function in ie6~ie8,
that's why?
thx

Hi,

I am using the following code to generate a temporary window:

In the js:

Code:

var win=null;
function NewWindow(mypage,myname,scroll){
settings='width=850,height=500,top=200,left=50,scrollbars=yes,location=yes,directories=no,status=no,menubar=no,toolbar=no,resizable=yes';
win=window.open(mypage,myname,settings);
if(win.focus){win.focus();}}

function hidestatus(){
window.status=''
return true
}

And in the HTML:

Code:

<a href=\"http://www.support-focus.com/check.php?key=$sup_cd2\" 
onclick=\"NewWindow(this.href,'','yes','default'); 
return false\" onfocus=\"this.blur()\" >

This code works , but I don't understand the mis-match or parameters

This is passing four param:
onclick=\"NewWindow(this.href,'','yes','default');

But this is only receiving three:
NewWindow(mypage,myname,scroll)

Is the last one (default) not counted for some reason ?


The was able to move the scroll param (yes) out

With this:
onclick=\"NewWindow(this.href,'','default');

and

NewWindow(mypage,myname)

Which now leaves just two params and a default.

Does anyone know why this appears to be unbalanced and also what the
myname param does? ( do I need it ? can I get rid of the '' and the myname ? )

Thanks

Hi,

I inherited an html demo (used to show customers our product w/o being connected to a server). Was going through the Html files to update the dates and fields and it seems that on some html files, when I change a date <td>08/11/2008 </td> to <td>08/11/2011</td>, save and refesh, I start getting a bunch of JS errors when I try and log back into the demo. I'm not changing anything in the JS files, so I don't understand why the errors are occuring.

I have a bunch of html files to change, and now, no matter which file I change (the dates, sample names, etc), I lose functionality on that particular page.

I'm beyond frustrated with this - I've modified similar demos at other companies and never had a problem.

Appreciate the help and assistance!

Ive searched on this board but cant find out why this doesn't work.

Code:

<script type="text/javascript">
function showSelected(val)

	if (val == "Nil")
	{
		document.getElementById('JustText').innerHTML='hi'
	}
	else
	{
		document.getElementById('selectedResult').innerHTML="<a href='mailto:" + val + "'>" + val + "</a><p>"
	}
</script>

What can I do to find out what the errors in the error console mean?

This is a little hard to explain so I'm posting an example.

Code:

//NESTED FUNCTION I'M USING TO DEMONSTRATE MY QUESTION
function foo(a) {
this.x = 5;

//USED TO SET THE VALUE OF X
if( a == 0 ) 
   return function(z) {
      return x = z;
   }

//USED TO RETRIEVE THE VALUE OF X
else if( a == 1 )
   return function() {
      return x;
   }

}


//MAKES setX THE SETTER FUNCTION
var setX = foo(0);
//MAKES getX THE GETTER FUNCTION
var getX = foo(1);

print( "setX(25), not an instance: " + setX( 25 ) );
print( "getX(), not an instance: " + getX() );

print( "" );
//CREATES AN OBJECT INSTANCE USING FOO AS CONSTRUCTOR
var q = new foo();
print( "value of x in object instance: " + q.x );
print( "" );

print( "setX(25), not an instance: " + setX( 25 ) );
print( "getX(), not an instance: " + getX() );

This code will output:
Code:

setX(25), not an instance: 25
getX(), not an instance: 25

value of x in object instance: 5

setX(25), not an instance: 25
getX(), not an instance: 25

Observations:
It seems like this.x actually has two meanings.
1)x becomes a member of the "Function" object foo().
2)x becomes a part of the constructor for prototype class foo.

But why then does x revert back to the original value of 5 when I use foo as a constructor? Does javascript automatically save the original value on creation for a reason?


What is going on behind the scenes to make this happen? Is this behavior part of an ontological model that makes sense?


Similarly, if I change "this.x" to "var x" I can access the value of x but I can't change it. Not that that I should be able to, the syntax "var x" doesn't make x a member of foo anyway. But I'm still having trouble classifying the relationship "var x" has to the function. Anyways this is more of a tangent. My main question is above but if anyone has something to say about this, I'd be interested to hear it.

It seems like all these behaviors have rules to them, but there is no conceptual model to think through that guide these behaviors. Or maybe I'm just ignorant. Enlighten me.

HI all - I am updating a website at my new place of work, changing the form they have for requesting information on the company.
I am trying to understand some JavaScript I found while googling forms. I am unsure of the significance of the following vertical code marks preceeding the form.name.value:
Code:

var msg = "form.name.value = "+document.registar.name.value;
alert(msg);
 var form = document.registar;
 if (form.name.value=="Name"
   || form.name.value == ""
   || form.email.value == "E-Mail Address"
   || form.email.value == ""
   || form.phone.value == ""
   || form.password1.value == ""
   || form.password2.value == ""
   || form.selection.value == ""
   || form.sq_answer.value == "Question Answer"
   || form.sq_answer.value == ""
   || form.radanswer.value == "") {
  window.alert("You must enter all fields above.");
  return false;
 }
else
  return true;
}

Thanks in advance.
Rick

I want to have another go at Javascript. I have several books on the subject but I find that my eyesight is a major problem. Therefore I want to try an on-line solution, preferably free.

I have Googled, but there are so many that I am almost dizzy with the choices.

Perhaps someone could recommend one. Not too fussy visually. My knowledge is VERY basic.

Frank

Hello! I am trying to find a script that allows you to open multiple browser tabs and then close each of those tabs, either one by one or all at once.

Does anyone know how to do this please?

Thanks so much for your help.

Does anyone know how to make URL links that use Javascript still work when
users have Javascript disabled on their browser?

The only reason I'm using JS on a URL is because my link opens a PDF file, and I'm forcing it not to cache so users have the latest version.

I tried the <script><noscript> tags, but I'm not sure if I'm using it
correctly, as my URL completely disappears.

Below is my HTML/Javascript code:

<p class="download">
<script type="text/javascript">document.write("<span
style=\"text-decoration: underline;\"><a href=\"javascript:void(0);\"
onclick=\"window.open(
'http://www.webchild.com.au/mediakit/Direct_Media_Kit_Web.pdf?nocache='+
Math.floor( Math.random()*11 ) );\" >The Child Magazines Media
Kit</a></span> (PDF 1 MB) ");</script>
<noscript><span style="text-decoration: underline;"><a
href="http://www.webchild.com.au/mediakit/Direct_Media_Kit_Web.pdf"
>The Child Magazines Media Kit</a></span> (PDF 1 MB)</noscript>
</p>


Thanks for any help,
Michael

Hi,

I have the following code snippet:
test.html
======
<script language="javascript" type="text/javascript">
var testVariable = "test";
</script>
<script language="javascript" type="text/javascript" src="test.js">
</script>

test.js
=====
var testVariable = window.top.testVariable;

In firefox, I'm able to access testvariable defined within test.html in test.js.

But in chrome, test.js couldnot get the window.top.testVariable field defined in test.html.

Can any one please let me know how i can make it work in chrome?. Am i missing something here?.

Hi Guys,
I am new at JavaScript and start to do some tutorials.What I am trying to do here is prompting user to input a name and if the name was valid the page(document) will display with all objects like the button.But if user enter a wrong name then the button will be disabled!
I create the following code but it did not work

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>New Web Project</title>
<script language="JavaScript" type="">
function changeColor(){
document.bgColor = "Gray";
}
</script>
</head>
<body>
<script language="JavaScript" type="text/javascript">
var person = "";
person = prompt('What is Your Name:');
if (person == "Foo") {
document.write("<h1 />Welcome " + person);
document.bgColor = "Yellow";
}
else {
document.write("<h1 />Access Denied!!!!");
document.bgColor = "Red";
document.getElementById("gree").disabled = true;
}
</script>

<div>
<p/><input id="gree" type="button" value="Gray " onClick="changeColor();">
</div>
</body>
</html>

as you can see I used the:
document.getElementById("gree").disabled = true;
but it did not work , could you please give an idea how I can solve this problem?
Thanks