Using The Switch Statement And Variable Scope?
Jun 14, 2010
I've created a jQuery script that uses a switch statement. However, my experience with it, relative to variable scope, doesn't seem to follow the logic.According to the JavaScript/jQuery theory, a global variable was accessible (meaning read & write) throughtout any function within any script (one that page).However, apparently that theory wasn't completely true as it pertained to switch statements that contained variables. To illustrate my case in point, I've included a simplistic version of my code:
$("#selector").delegate("div", "click", function(event) {
var testVar = 4;
switch (this.id) {
[code]...
As shown, the variable "testVar" is not accessible from one case to the next case .Furthermore, to add insult to injury, I am seeing the same behavior within the conditional if else statement counterpart to the switch statement.
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Nov 1, 2005
This is my first time using the switch statement. I would appreciate your suggestion on how to do this properly. I am trying to get customer age which is (age) and compare it with the monthly rate then the text msg will display in the textarea. Also, I am having trouble figuring out how I can defined my monthlyRate in the switch or do I need to this outside of the switch? Code:
}
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Aug 4, 2007
Is it possible to create a Switch Statement in a URL? If so, how? This is what I have so far:
<html>
<body>
<head>
<center>
<Script Language="JavaScript">
function load() {
var load = window.open(http://www.xxx.com/123456789,'','scrollbars=yes,menubar=no,height=600,width=800,resizable=yes,toolbar=no,location=no,st atus=no');
// -->
</Script>
</head>
<br><a href="javascript:load()">Link!</a>
<br><br>
</body>
</html>
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Jan 17, 2010
Assignment:
Switch Create a HTML that uses Javascript. Create a page that tells a student the range their mark falls in if they know their letter grade. Below 50 is an "F", 50-59.9 is a D, 60 - 69.9 is a "C", 70 - 79.9 is a "B", 80 - 89.9 is an "A" and 90 - 100 is an "A+". You determine the input and output format.
<html>
<!DOCTYPE HTML PUBLIC "-W3CDTD HTML 4.01EN">
<head>
<title>Switch</title>
[Code]....
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Jul 18, 2006
I need to write the switch statement below in a way where I can have each case with multiple values, and avoid using "break;" to allow the evaluation of the rest of cases. the code below should jump into the first 2 cases but not the last one, but it is not doing that. Is there a way for me to get around this.
function test(){
var Temp = 'cs1'
switch(Temp){
case 'cs1' , 'cs2':
alert(Ƈ');
case 'cs1':
alert(ƈ');
case 'cs2':
alert(Ɖ');
}
}
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May 4, 2011
how to display images according to switch statement value...
for example if case value is rose it has to display rose picture that is stored in our system.
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Oct 19, 2010
I'm trying to code a script that will display an approximate postage price based on different combinations of variables, but the numbers I defined for each case aren't reflected in the text box. I'm using a switch statement for all the different combinations of options, which the user will choose by selecting check-boxes. (Additionally, I know that this code probably isn't a very efficient way of doing what I'm doing - how to improve it.) I've attached all the relevant parts of the code, including how I defined variables originally.
<script type="text/javascript">
function count(){
var firstclass = document.calc.firstclass.value;
var postcard = document.calc.firstclass.value;
var numpages = document.calc.numpages.value;
var nms = document.calc.nms.value;
var large = document.calc.large.value;
var numpages = parseInt(document.calc.numpages.value); .....
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Oct 6, 2011
I am trying to figure out where I went wrong in my code. The objective is to display all lines of the song using a switch statement. I thought I had my head wrapped around it, but apparently not.
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Sep 14, 2010
how to get this functionality going. I have a div name "footer". Within "footer" I have 4 links:
link1, link2, link3, link4
Is there anyway to write a function which will sense which link was clicked and then alert the id of that selected link. I have written the code but am not certain why isn't it working. here is my code.
$('#footer a').bind('click', function(){
//alert($(this).attr('id'));
var mId = $(this).attr('id');
switch(mId)
[Code]....
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Nov 14, 2009
Im creating a switch statement for this case, but dont know how to start - Create a Switch statement that tests the value of the partyType parameter. If partyType equals "D", store the following text string in a variable named barText: <td class='dem'> </td>
If partyType equals "R", barText should equal <td class='rep'> </td> etc.. So since its going to test the value of the partyType parameter, and store the text string in a variable named barText do i begin like:
[Code]...
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Feb 24, 2011
i would like to check for the window size with jquery and based on the different resolutions i would like to change the background image. So i was thinking to somehow use the "switch" statement for more cases, but i just don't know how this would look like. This is the basic structure i want but with more options:
if ((screen.width>=1024) && (screen.height>=768)) {
//do something
}
[code]....
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Jul 20, 2005
If I do . . .
myForm=document.tstForm;
function initialSetup(){
myForm.fld01.value="Test 01"
myForm.fld02.value="Test 02";
myForm.fld01.focus();
}
Then, in the body tag, I do onLoad="initialSetup()",
the script doesn't work and I get a "myForm has no properties" error
I know it'll work if I move it within the function, but I figured a
global variable would retain its value within the function. Why not?
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Jul 23, 2005
Given the following working code:
function attributes() {
var attr1 = arguments[0] || '_'
var attr2 = arguments[1] || '_'
return (
function (el1, el2) {
var value1 = el1[attr1] + el1[attr2];
var value2 = el2[attr1] + el2[attr2];
if (value1 > value2) return 1;
else if (value1 < value2) return -1;
else return 0;
}
);
}
var a = [
{ a:'smith', b:'john' },
{ a:'jones', b:'bob' },
{ a:'smith', b:'jane' }
];
a.sort(attributes('a', 'b'));
for (var i =0; i < a.length; i++) {
document.write(a[i].a + ', ' + a[i].b + '<br>');
}
My question is, are attr1 and attr2 guaranteed to exist through
the lifetime of a.sort(attributes('a', 'b'))?
As I understand it, the anonymous inner function reference I am
returning is a property of attributes(). As such, when I return a
reference to the anonymous inner function, the outer attributes()
function must continue to exist (as must attr1 and att2) until
there are no further references to the inner anonymous function.
As a result, there is no danger of attr1 or attr2 "disappearing"
during the repeated calling of the anonymous inner function.
Is my explanation basically correct, or am I deluding myself and
I'm just lucky that the garbage collector hasn't recovered attr1
or attr2 while the sort is still going on? In other words, is the
behaviour I'm seeing consistent and predictable, or should I
change my approach?
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Oct 30, 2006
I think I've had JavaScript variable scope figured out, can you please
see if I've got it correctly?
* Variables can be local or global
* When a variable is declared outside any function, it is global
regardless of whether it's declared with or without "var"
* When it is declared inside a function, if declared with "var", it's
local, if not, it's global
* A local variable that is declared inside a function is local to the
whole function, regardless of where it is declared, e.g.:
function blah() {
for(var i ... ) {
var j ...
}}
i and j will both be visible within blah() after their declaration.
* the notion of "function" in this context also applies for this kind
of construct:
var myHandler =
{
onClickDo: function()
{
in the sense that whatever one declares inside onClickDo with "var"
will only be visible inside onClickDo. What else, am I missing anything?
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Oct 17, 2010
I have this web application where users are able to fill out and submit reports. The reports and scripts are part of a whole system, that is, they are used on a couple of different clients written in both vb and c#. This is the web-version of those clients.The scripting language is javascript and is executed using different script engines on the different systems. But for the web-version it is just executed in the browser.The different fields in the report can be accessed by typing:ID1.value. To get ID1 to apply for the input-field with id ID1 I had to in the initfunction of the page write a window["ID1"] = document.getElementById("ID1");
But my problem is when this element change. Cause in the report I have a special element that in the browser is translated to a table-element with a report-field in each cell.When I switch the current row, I need to update the window["ID1"] to equal the correct report field on the selected row. But when trying to access the new variable ID1 from a buttons onclick event it is undefined.<input type="text" id="test" onclick="alert(ID1.value);" />What I think happens is that when the page is first drawn the onclick event is created and as I understand, variables inside an event has the same value as when the event was created.
So if ID1.value was something when the page was created it will be the same when it is called even if the value of ID1 is different. And that seems to be the case. When I debug the page, before entering the event, ID1.value has the correct value while inside the event it is undefined and after the event it has the correct value. If I write window["ID1"] correct value is also shown.But a weird thing is that in another place in the code I had the same problem but instead of having the code inside the onclick event I first had a global function changeActiveRow and inside that I had an eval, eval(document.getElementById("ID1_script")) where ID1_script is a hidden element whos value is a script using ID1.value and that works.
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Nov 23, 2005
I am trying to convert some of my javascripts into a class and am
running into difficulties which i think are related to variable scope.
Basically I have a constructor function for a calendarInput class that
takes 4 parameters, the first is a reference name/number for this
input. I also have some functions for importing my PHP classes into
Javascript using AJAX (properties only. still trying to get methods
working but that's another story!). The relevant function is called
call_object_method(classname, methodname, createparams, methodparams,
post, callbackfunction). This creates an instance of the specified PHP
class using the parameters in createparams. It then calls the
specified method using the parameters in methodparams. The result is
passed back to the javascript function specified in the callbackfunction parameter (ie the value of xmlhttp.onreadystatechange is set to callbackfunction before xmlhttp.send() is called)
The function i am trying to fix is called show (x,y) which creates the
html for the calendarInput and displays it at co-ordinates x, y.
So, my code is as follows:
function calendarInput(calendarid, target, displaytarget, value)
{
this.calendarid = calendarid;
this.target = target;
this.displaytarget = displaytarget;
this.value = value;
this.show = function(x, y)
{
<!--// bunch of init and prepping code. includes creating
createparams and methodparams arrays //-->
call_object_method("cms_calendar", "getcalendarview",
createparams, methodparams, false, this.showcallback);
}
this.showcallback = function()
{
alert(this);
<!--//code to create html//-->
}
}
I know i've cut out most of the innards of this. This is because I
have already tested these functions and had the calendarInput working
outside of a class, hence am pretty sure that this is ok (plus it runs
to almost 1000 lines these days!!). My problem is that when I call the
show method, the alert on the first line of the callback function
returns the function showcallback instead of (as i was expecting) the
instance of the calendarInput object. Whilst this kinda makes sense I
can't figure out how to reference the Object instead. I have tried
'this.parent' but this returned undefined. I have tried changing the
way i reference the callback function (ie the final parameter of
call_object_method) but no joy.
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Aug 23, 2010
I've recently started developing javascript using jQuery and so far I'm really enjoying it.Being a professional programmer (mainly C, C++, java and python) there is one thing that's been puzzling me regarding variable scope and unnamed function declarations. Let me exemplify:
------------------------
var sum = 0;
$(xmlobj).find("item").each(function(){
[code]....
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Oct 27, 2009
I'm just starting out with Javascript as a development language and this will probably be a relatively simple problem for someone to solve for me.
I am trying to access a variable (this.bodyEl.innerHTML) from within a function but get an error message indicating that it is "undefined". I know that it is a valid variable because I call it elsewhere outside of the inner function itself.
I'm sure this is just a scope issue, but I'd welcome any suggestions on how to solve it with an explanation of where I've gone wrong if you have the time.
[Code]...
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Jan 31, 2011
[code]how i can set context/scope for myStartAction so it can access (this.url) variable?console.log(dd.url) will work but i can't predict what name will object have (that depends on user) there might be more than one instance of myObject
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Jul 25, 2011
I think the last thing people seem to learn about in JavaScript when they're not coming from other programming languages is variable scope. Some even get all the way into AJAX without having learned about scope, and this is a time when it's really needed. Although the scope of JavaScript variables is non-complex by nature, it's something we should all get a full understanding for before we move too far.
Section 1: What is "scope"?
Section 2: The "var" keyword
Section 3: The "this" keyword
Section 4: Closures or "Anonymous functions and self-invoking closures
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Apr 12, 2011
I'm writing an image gallery script in which the thumbnail for the currently-viewed image is indicated with a smaller image below the thumbnail. My placeholder is as follows:
<img name="indicator0" alt="indicator>
with indicator1, indicator2, etc. following, one below each thumbnail. In my script, which placeholder has the indicator is called by the variable thumbIndicator. I'd like to be able to do that like this:
document.(thumbIndicator).src = "indicator_image.jpg";
but this has not worked. I've also changed my image placeholder to this:
<img id="indicator0" alt="indicator">
and the script to this:
document.getElementByID(thumbIndicator).src = "indicator_image.jpg";
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Mar 23, 2010
I am using Ben Alman's JQuery resize plugin in order to obtain the varying computed width of an element when the window is resized (the element in question is a page wrapper that exhibits the expand-to-fit behavior of a block box, and it's computed width is obviously influenced by the resizing of the window. Essentially, what I need to be able to do, is to reference a variable that is defined in a .resize() function ('width_page') in a seperate .each() function.
[Code]...
I now understand that variables can't cross boundaries like in the example above, which leaves me a little stuck. I also understand that this is specific to the context of the .resize() function, and that it can't be taken out of it without using an element selector. Is there some way I can call the .resize() function in my .each() function?
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Jun 17, 2010
Need to apply a var to a statement if its conditions are met, this syntax isn't throwing errors but its not working.
<script type="text/javascript">
$(document).ready(function(){
var action_is_post = false;
//stuff here
[Code].....
should I use something other than .ready? I need it to apply the var when #stepDesc0 has the class current.
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Apr 17, 2011
I'm having a tough time trying to add the "zip" variable to my YQL statement.
var zip = $(this).attr('zip');
$.YQL("select * from rss where url='http://weather.yahooapis.com/forecastrss?p=' ' "+ zip +" ' ", function(data){
var w=data.query.results.item;
[Code].....
I've tried as many different ways as I could imagine. Simply putting the literal zip code in the query works perfect.
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Mar 10, 2009
Is it possible to pass a variable into a if statement, What I mean is the function takes in variables i need to take one of those variable and put it in the actual statement.I need the check variable to be put in the if statement but all it does is throw an error because it can't find "check".
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Oct 22, 2010
I have been assigned the old Pizza Form tutorial. My form asks for customer info, select size with radio button, and select toppings with checkboxes.I created a ValidateForm() function to check if these are filled in and output a message for each field saying "please fill in field."My problem now is that on Submit I need to print out a message with customer info, selected size, and selected toppings.I have the customer info done with a var message:
var message = "Name: " + name + "
";
message += "Address: " + address + "
[code]...
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