load javascript after the html has rendered - javascript

The below script works perfectly fine if the p tag is placed above and script placed below
<p id="dom_intro">Hello</p>
<script>
x=document.getElementById("dom_intro");
document.write("<p>This is the text of dom intro" + x.innerHTML + "Howzzat </p>");
</script>
If the same code where the script is placed first and html p tag is placed below the script it does not work, I am getting error x is null or undefined
<script>
x=document.getElementById("dom_intro");
document.write("<p>This is the text of dom intro" + x.innerHTML + "Howzzat </p>");
</script>
<p id="dom_intro">Hello</p>
I tried pasting the script in external javascript file and placed at the head section
I am getting the same error. Is there any javascript or jquery script to load the javascript file after the html has rendred

jquery:
$(document).ready(){function(){
//yourcode
});
And Javascript
window.onload=function(){
//your code
}
The document ready in jquery executes the function when the DOM is ready, that means before some images are downloaded.
Window.onload is fired when page is completely ready, that is when all images are finished loading.

you need to access the element once the dom is ready. you are getting this error because your trying to access the p tag before the dom getting loaded.
this may fix your problem
window.onload = function(){
// your javascript here
x=document.getElementById("dom_intro");
document.write("<p>This is the text of dom intro" + x.innerHTML + "Howzzat </p>");
}

Browsers are rendering your code as they see it (lineary). The here problem is that your script tries to access something that doesn't exists yet so it's common practice to wait until all DOM elements are ready and then execute script.
Please look here: http://api.jquery.com/ready/
$(document).ready(function() {
// Handler for .ready() called.
});
Which is equivalent to calling:
$(function() {
// Handler for .ready() called.
});

The <script> content is executed where you place it, so in the second case, you are trying to use "dom_intro" before it is declared. But you're trying to load the javascript AFTER the html has rendered, so you don't want to write the script BEFORE the html content, right?
The usual way to load JS files are just before the </body> close tag. That way you'll be sure that any html won't be downloaded before all your HTML is loaded.
And if you want to wait for the HTML to finish loading before executing any JS, you must do something like this:
Plain javascript:
window.onload = function () {
// do_whatever_you_want
}
Jquery:
$(document).ready(function() {
// do_whatever_you_want
}

Related

javascript onclick null in custom js file

I'm trying to simply detect clicking an A link to display an Alert box. Whenever I place the script inside the php file my a link is located, it works fine, but whenever I place it in my custom JS file, it doesn't detect it, and I get the error 'Uncaught TypeError : Cannot set property "onclick" of null'.
The link between the php page and custom js page is definitely working, as I have previous working code on the page. It simply wont detect my A link it its located in an external script.
HTML
<a id="ConfirmHolidayClose" href="#">
<img src="assets/img/close-button.png" alt="Holiday-request-close-button"
class="CloseButton" />
</a>
JAVASCRIPT
document.getElementById("ConfirmHolidayClose").onclick=function(){
alert("Working");
}
UPDATE - Forgot to mention sorry, my a link is nested inside div called 'ConfirmHoliday'.
I have JS code manipulating the ConfirmHoliday div inside my Custom JS, so it cant be loading after because it is finding its parent div perfectly well at the moment.
The javascript file runs before the element is created, thus it doesn't exist. To solve this, you have couple options:
1) Surround the code with a window.onload function
window.onload = function () {
// Your code here
};
2) Put it in a separate js file and add a defer property to the script tag.
<script src="yourScript.js" defer="defer"></script>
3) Put the script tag after the anchor tag
It's trying to access the ConfirmHolidayClose element before it exists maybe? Where is your JS loaded in your page? I'm guessing in your <head>
A few solutions:
1) Move your script to bottom of page just above </body>
2) wrap your JS in dom ready function, this ensures no JS will run until the DOM tree exists. Easiest with jQuery, example below...
jQuery example
$(function() {
document.getElementById("ConfirmHolidayClose").onclick=function(){
alert("Working");
}
});
Vanilla example
document.addEventListener("DOMContentLoaded", function() {
document.getElementById("ConfirmHolidayClose").onclick=function(){
alert("Working");
}
});

Initialize more than one html element using jQuery and Javascript

I have tried to lead my html element to fire my customized JS file's method.
Third textarea appears nicely.
First and second textareas does not effect any of the settings i am trying to change in myJSFile.js file.
Here's my problem : js file loads the last textarea nicely, but cannot initialize previous ones properly using my js methods.
I'm doing something wrong with my JS file, and i'd appreciate if you help me.
P.S. : Initalizing some plugin and working on CKEditor.
Here's my HTML file :
<textarea id="myTextAreaID" name="myTextArea"></textarea>
<script type="text/javascript" src="../public/js/myJSFile.js"onload="setTextAreaValues('myTextAreaID')"></script>
<textarea id="myTextAreaID2" name="myTextArea2"></textarea>
<script type="text/javascript" src="../public/js/myJSFile.js"onload="setTextAreaValues('myTextAreaID2')"></script>
<textarea id="myTextAreaID3" name="myTextArea3"></textarea>
<script type="text/javascript" src="../public/js/myJSFile.js"onload="setTextAreaValues('myTextAreaID3')"></script>
Here's myJSFile.js file
var textAreaID;
$(function(){
var myTextArea = $('#'+textAreaID);
//something is being loaded here, and it is loaded fine.
});
function setTextAreaParameters(param){
textAreaID = param;
}
Thanks in advance.
This is not very good idea to do it like this, however it's interesting to understand why it happens. In your code below you are defining global variable textAreaID:
var textAreaID;
$(function() {
var myTextArea = $('#' + textAreaID);
//something is being loaded here, and it is loaded fine.
});
function setTextAreaParameters(param) {
textAreaID = param;
}
This script is injected three times into document. After the last script tag the value of textAreaID variable will be myTextAreaID3, because it's global and the last setTextAreaParameters invocation will override previous. Remember that scripts are loaded synchronously in your case (no async or deferred attribute), it means that onload callbacks don't wait and immediately set textAreaID to new values.
However DOMContentLoaded event has not yet fired. This is the event you are subscribing with this code:
$(function() {
// DOMContentLoaded
});
When it eventually does - only the third textarea will be processed - the one with id myTextAreaID3.
Better approach would be to have only one script tag and set textareas the same className attribute:
<textarea id="myTextAreaID2" name="myTextArea2" class="editor"></textarea>
Then in the script probably have some sort of map with configuration parameters for each individual textarea.
You are including the same script three times, but the browser is probably smart enough to only load it once (no reason to load the same script on the same page more than once).
What you need to do is to include the script only once, say before the end of the body tag
...
<script type="text/javascript" src="../public/js/myJSFile.js"></script>
</body>
and then in the JS file, wait for the document to load, and handle all text areas accordingly:
$(function() {
$('textarea').each(function(i, j) {
console.log('do something for the ' + i + 'th text area');
});
})

Javascript adding <script> tag after page loads

Got a little problem here. Basically, I'm trying to add a script tag after the page loads.
This is what I am doing:
index.php:
<html>
<head>
<script src="//ajax.googleapis.com/ajax/libs/jquery/1.10.2/jquery.min.js"></script>
<script>
function getad()
{
$.post('assets/getad.php', "ad", function(response) {
response = response.replace('document.write','document.getElementById("ad").innerHTML = ');
eval(response);
console.log(response);
});
}
getad();
</script>
<div id="ad"></div>
</body>
</html>
getad.php:
<?php
echo file_get_contents("http://ads1.qadabra.com/t?id=a823aca3-9e3c-4ddd-a0cc-14b497cad85b&size=300x250");
?>
You can find a demo here: http://dev.cj.gy/game/
As you can see, the #ad div DOES get filled with the correct script tag, but it doesnt actually run, If I edit the page to include the script tag right at page load, it does run.
Yes, <script> tags cause execution when parsed as part of the main document; they don't execute from being written to innerHTML.
You can create an executing script element outside of that initial parse using the DOM method of calling createElement('script'), setting its src/content and adding it to the document. This is what jQuery's getScript does.
However it wouldn't do you much good because the next script, that ads1.qadabra.com is document.writeing to the page, also itself calls document.write.
You could work your way around both of these calls at the client side (ie without getad.php), by assigning your own custom function to document.write that, instead of writing to the loading page, attempts to extract the source of the script tag passed to it, and load that in a DOM-created script element.
But in general these are scripts designed to work synchronously at document load time; anything you do to try to force them to run in a way they weren't intended to is likely to be fragile and stop working when the ad network change anything.
If you want to load a third-party ad without pausing the loading of the parent document, I suggest putting it in an iframe.

Can someone explain to me how this is possible? (Picture in comments)

So I'm trying to link up my html and javascript files in notepad++, but it isn't working properly.
I wanted to know how it is possible that it writes test, but doesn't remove the div. Can anyone explain this? Thanks in advance!
1, jQuery isn't linked. Meaning, you don't have <script type='text/javascript' src='myjQueryfile.js'></script> in your HTML, you'll want to put it before your script.
2:
Because the element with the ID of blue, doesn't exist yet. The DOM - basically the object of your HTML - has yet to be constructed when your script is run, which in this case is the top of the page, before blue comes into existence. You'll want to use an event to fix this, typically $(function(){ ... }); which will execute your code when the DOM is ready.
Also, document.write just writes code then and there, meaning exactly where the document.write calls is made, the HTML will be outputted.
You should have linked jquery. You're trying to use it without having it linked.
The script is loaded in the head. At the time the script executes the body of the document is not built, so nothing is removed. If you were to use the document.ready callback (and had properly included jQuery) it would work
$(function(){ $("#blue").remove(); });
A plain js version of this is
window.onload = function(){
var b = document.getElementById("blue");
b.parentNode.remove(b);
};
At the time the script runs, only the portion of the document up to the <script> tag has been loaded. You need to delay until the DOM has fully loaded before the script can target the DOM:
document.addEventListener("DOMContentLoaded", function(event) {
$("#blue").remove();
});

Call a javascript function after loading the Div

How to call the javascript function, after loading the particular div?
Typically, JavaScript execution is deferred till after the entire document is loaded by using the window.onload event.
window.onload = function() {
// Do stuff
};
Otherwise, if you don't want to or if you have no need to wait for the entire document to load, you can include your JavaScript directly after the closing tag of the element (div) which you are concerned with.
<div>
...
</div>
<script src="blah-blah-blah.js"></script>
I'd check if div exists in DOM like this :
javascript
if(document.getElementById('myDiv'))
or jQuery
if($("#myDiv"))

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