javascript function call not working - javascript

Inside register.js I have a function called username() and I want to call it from my webpage but the function will not run.
Here is where I include the .js file and call the function:
<head>
<link rel="stylesheet" href="css/base.css" />
<script src="resources/jquery-1.8.1.min.js"></script>
<script src="resources/register.js"></script>
<script type="text/javascript">username();</script>
</head>
This is in the .js file:
function username(){
document.getElementById("username").innerHTML="Username already in use";
}

This is a common mistake from folks just starting out in Javascript. Trouble is, if you don't know what to call it, it is hard to search for the answer.
What is happening: When the <head> element is processed, nothing in the document body exists yet. Your element username doesn't exist, so the getElementById fails.
Solution 1 Move <script type="text/javascript">username();</script> to just before the </body> so everything will be in place.
Solution 2 Use the onload event to run your Javscript after everything else runs with a
<body onload="username()">
(jQuery has its own onload event handling as well.)

You have no element with the id username.
(You might have one lower down in the document, which you haven't shared with us, but since you are calling the function directly (and not in response to an event, such as load) while still in the <head> it won't yet exist.)

Related

Calling javascript function from js file does not works

I have a simple javascript function on my page that works well, but I decided to move it away from index.html to a seperate js file.
The problem is that I cannot get it to execute from that seperate file.
This has been asked many many times here and the solution is always the same, but it just wont work for me. Also on google I can find lots of examples but they simply do not work for me. I tried many of them but with no luck.
So I must be missing something obvious I guess.
This is the header of my index.html
<?php session_start(); ?>
<html>
<head>
<title>Test</title>
<link rel="stylesheet" href="test.css">
<script src="gttJSFunctions.js" type="text/javascript"></script>
</head>
<body>
...
The function in gttJSFunctions.js is called Logout()
As I said it works perfect when I put it inside my index.html, but I cant get it to execute from the seperate js file
this is the entire content of gttJSFunctions.js
<script language='JavaScript'>
function Logout()
{
conf = confirm("Are you sure you want to logout?");
if (conf)
{
window.open("logout.php", "_self");
}
}
Can someone please point out what I am doing wrong.
Your external JavaScript file should contain only JavaScript. No tags.
Just remove the <script language='JavaScript'> from your file and you are good to go.
Remove <script language='JavaScript'> from your gttJSFunctions.js file because it's already a Javascript file, you don't have to specify it.
Best practice: put <script ... /> tags at the bottom of your code, just before the </body> tag. It will improve your page speed and also, as Archer told, avoid you to deal with the DOM ready common mistake.

HTML Page life cycle JS execution order, with document ready execution

<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<title></title>
</head>
<body>
abc
<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.1.1/jquery.min.js"></script>
<script src="Scripts/first.js"></script>
<script src="Scripts/second.js"></script>
</body>
</html>
//first.js
$(document).ready(function () {
alert(first.firstChild.firstGrandChild);
})
//second.js
var first = {
firstChild: {
firstGrandChild: false
}
}
I have simplified the problem here. We have html page that has reference to two js-first and second. So i assume browser would render html first, stop to download first js, then download second js.
Then document ready of first js would be executed which will get first.firstChild.firstChildChild of second js.
I have few questions:
What would be execution order of html execution, download js, document ready execution of fist js, document ready execution of second js (if it has doc ready)?
Now i am able to access these objects from first js but in very similar scenario in my production app, i get these as undefined sporadically. What could be possible reason for that?
If i have circular dependency b/w first and second js and i want things to functions smoothly, what should i do? (example fist js calling second js methods from document ready and from outsid doc ready too AND vice-versa)

Best way to access external JavaScript file and place contents in div?

So, lets say you have a page that wants to load from a javascript file and it includes
temp.html file
<script src="example.js"></script>
<p class="one"></p>
Now in the example.js file you have a function that is
function getInfo() {
var place = "foo"
$(".one").html(place);
}
//Edit currently I call the function inside the JS file
getInfo();
My question is how would you connect the two files so that the external javascript file knows that it is pointed to the paragraph with the class one?
Normally when this is in a single page, you would call the function and the info will be set.
I have seen a getScript method and a load method for Jquery. Would that be applicable here?
Any ideas on how to approach this? If you provide some code that will be super helpful.
Thanks in advance.
Looks like you want to execute getInfo() as soon as it's defined (i.e.: example.js is loaded).
You can try this approach:
<script src="example.js" onload="getInfo();"></script>
In your example.js, change getInfo() to something like this:
function getInfo() {
$(document).ready(function() {
var place = "foo"
$(".one").html(place);
});
}
Your language is confusing, but you could use jQuery's $(document).ready function which would suffice. Generally speaking, an externally loaded file should execute where the tag is in the script.
A hack could be to place a tag before the end of your document body, give it an id, and then use $('#id').ready() there. In general though, you could just try coding the transclusion concept (I'm guessing you're used to this) from scratch using intervals and timeouts.
<div id="rdy">
</div>
</body>
Then in your file:
$('#rdy').ready(getInfo);
Just my added opinion, you should consider that Google is up to some not-so-nice things these days, they are long-gone from the "do no evil" mantra.
If we assume you have a JavaScript file that contains this content:
function getInfo() {
var place = "foo"
$(".one").html(place);
}
then your markup will look something like this:
<html>
<head>
<meta charset="utf-8" />
<title></title>
<script src="//code.jquery.com/jquery-1.11.0.min.js"></script>
<script src="example.js"></script>
<script>
$(function(){
getInfo();
});
</script>
</head>
<body>
<p class="one"></p>
</body>
</html>
$(function(){ ... }); is just the simplified version of $(document).ready(function(){ ... });. They both more or less handle the onload event, which fires when page has finished loading.

How to detect whether a plugin or script has already been loaded without using eval() or requireJS?

I'm working on a plugin that allows to inject 3rd party code into a page (either as iframe or directly into the DOM).
My problem is "direct injections", because I need to make sure, I don't add any <scripts> additional times, if they are needed in my main page and in a page I'm loading and injecting.
For example (and I can't use requireJS), my page.html looks like this:
<html>
<head>
<script type="text/js" src="jquery.js"></script> // exports window.$
<script type="text/js" src="foo.js"></script> // exports window.foo
</head>
<body>
<!-- things that make foo load anotherPage.html and append its content here -->
</body>
</html>
with anotherPage.html
<html>
<head>
<script type="text/js" src="foo.js"></script> // exports window.foo
</head>
<body>
<!-- stuff that also runs on FOO -->
</body>
</html>
Page loading is done via Ajax and when I'm processing the data returned by my request for anotherPage.html I end up with a list of all elements after doing this:
cleanedString = ajaxResponseData
.replace(priv.removeJSComments, "")
.replace(priv.removeHTMLComments,"")
.replace(priv.removeLineBreaks, "")
.replace(priv.removeWhiteSpace, " ")
.replace(priv.removeWhiteSpaceBetweenElements, "><");
// this will return a list with head and body elements
// e.g. [meta, title, link, p, div, script.foo]
content = $.parseHTML(cleanedString, true);
// insert into DOM
someTarget.append(content);
This is where I'm stuck trying to detect whether a script I'm about to append to the document is already there.
I cannot go by the src, because the filename may differ and a script may be hosted on a different domain (with Access-Control-Allow-Origin correctly set). I also don't know, what and if the script I'm about to append returns a global I already have defined and I can't/don't want to use eval() to find out.
Question:
Is there any way to identify whether a plugin or script that may return a global is already "on" a page, when I only have the "non-appended" <script> element available?
Thanks!
here is an example of my self-enclosed module pattern, i call it a "Sentinel":
(function wait(){
if(!self.$){
if(!wait.waitingJQ){
wait.waitingJQ=true;
addScriptTag(JQUERY_URL);
}
return setTimeout(wait, 44);
}
doStuffThatNeedsJquery();
}());
The sentinel pattern work from anywhere (internal or external), doesn't care about script loading order, and works with ANY script loading library. you can list additional depends below the jQuery fork in the same manner, just put your greedy code at the bottom of the sentinel wrapper function.

jQuery $(document).ready () fires twice

I've been sifting around the web trying to find out whats going on here and I have not been able to get a concrete answer.
I have one $(document).ready on my site that seams to run multiple times regardless of the code that is inside it.
I've read up on the bug reports for jQuery about how the .ready event will fire twice if you have an exception that occurs within your statement. However even when I have the following code it still runs twice:
$(document).ready(function() {
try{
console.log('ready');
}
catch(e){
console.log(e);
}
});
In the console all I see is "ready" logged twice. Is it possible that another .ready with an exception in it would cause an issue? My understanding was that all .ready tags were independent of each other, but I cannot seem to find where this is coming into play?
Here is the head block for the site:
<head>
<title>${path.title}</title>
<meta name="Description" content="${path.description}" />
<link href="${cssHost}${path.pathCss}" rel="stylesheet" type="text/css" />
<script src="http://ajax.googleapis.com/ajax/libs/jquery/1.7.1/jquery.min.js" type="text/javascript" charset="utf-8"><!----></script>
<script src="media/js/fancybox/jquery.fancybox.pack.js" type="text/javascript" ><!-- --></script>
<script src="/media/es/jobsite/js/landing.js" type="text/javascript" ><!-- --></script>
<script src="/media/es/jobsite/js/functions.js" type="text/javascript"><!-- --> </script>
<script src="/media/es/jobsite/js/jobParsing.js" type="text/javascript" charset="utf-8"><!----></script>
<script src="/media/es/jobsite/js/queryNormilization.js" type="text/javascript" charset="utf-8"><!----></script>
<script src="${jsHost}/js/jquery/jquery.metadata.js" type="text/javascript" charset="utf-8"><!----></script>
<script src="${jsHost}/js/jquery/jquery.form.js" type="text/javascript" charset="utf-8"><!----></script>
<script src="http://ajax.aspnetcdn.com/ajax/jquery.validate/1.7/jquery.validate.min.js" type="text/javascript" charset="utf-8"><!----></script>
<script src="${jsHost}/js/jquery.i18n.properties-min.js" type="text/javascript" charset="utf-8"><!----></script>
<script type="text/javascript" charset="utf-8">
function updateBannerLink() {
var s4 = location.hash.substring(1);
$("#banner").attr('href','http://INTELATRACKING.ORG/?a=12240&c=29258&s4='+s4+'&s5=^');
}
</script>
</head>
Pay no attention to the JSP variables, but as you can see i'm only calling the functions.js file once (which is where the .ready function exists)
The ready event cannot fire twice. What is more than likely happening is you have code that is moving or manipulating the element that the code is contained within which causes the browser to re-execute the script block.
This can be avoided by including script tags in the <head> or before the closing </body> tag and not using $('body').wrapInner();. using $('body').html($('body').html().replace(...)); has the same effect.
It happened to me also, but I realized that the script had been included twice because of a bad merge.
This happened to me when using KendoUI... invoking a popup window would cause the document.ready event to fire multiple times. The easy solution is to set a global flag so that it only runs once:
var pageInitialized = false;
$(function()
{
if(pageInitialized) return;
pageInitialized = true;
// Put your init logic here.
});
It's sort of hack-ish, but it works.
Make sure you don't include JS file twice. That was my case
You might consider to use
window.onload
instead of
$(document).ready
try putting this in your functions.js to prevent it from being executed twice :
var checkit = window.check_var;
if(checkit === undefined){ //file never entered. the global var was not set.
window.check_var = 1;
}
else {
//your functions.js content
}
however i suggest that you look more into it to see where are you calling the second time.
I had a similar problem when I was trying to refresh a partial. I called a return ActionResult instead of a return PartialViewResult. The ActionResult caused my ready() to run twice.
There is a possibility to encounter this problem when you add same controller twice in the html.
For an instance:
[js]
app.controller('AppCtrl', function ($scope) {
$(document).ready(function () {
alert("Hello");
//this will call twice
});
});
[html]
//controller mentioned for the first time
<md-content ng-controller="AppCtrl">
//some thing
</md-content>
//same controller mentioned again
<md-content ng-controller="AppCtrl">
//some thing
</md-content>
I had a similar issue today. A <button type="submit"> caused the $(document).ready(...) event to fire again in my case. Changing the code to <button type="button"> solved the issue for me.
See document.ready function called again after submit button? here on stackoverflow for more details.
In my case $(document).ready was firing twice because of bad CSS, check if any part of your CSS has background-image: url('');
If the iframe doesnt show anything and is used for other reasons (like uploading a file without reload) you can do something like this :
<iframe id="upload_target" name="upload_target" style="width:0;height:0;border:0px solid #fff;"></iframe>
Notice that src is not included that prevents the second on ready trigger on the document.
I had this problem with window.load function was executed twice:
The reason was because I had reference to the same javascript-file in the main page as well as a .net usercontrol. When I removed the reference in the main page, the load-function was only executed once.
I had this happen to me this morning... and what I discovered after closely examining some html code in a jquery modal form that I had recently manipulated, that I'd accidentally removed a closing table tag. I haven't taken the time yet to fully understand why that caused the document.ready function to be called twice, but it did. Adding the closing table tag fixed this issue.
jQuery JavaScript Library v1.8.3 (yes, it is a legacy app)
My problem was that I had tags referencing my JS file in both my index.cshtml file AND my _Layout.cshtml. This was causing the document.ready function to fire twice, which was causing DataTables to bomb.

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