In the following html page i try to put script2 before footer. But this doesn't work. What's wrong?
<!doctype html>
<html lang="en">
<head>
<meta charset="utf-8">
<title>scrollLeft demo</title>
<script src="https://code.jquery.com/jquery-1.10.2.js"></script>
<script>
var script2 = document.createElement('script');
script2.text="alert('ΟΚ')";
document.body.insertBefore( script2, document.getElementsByClassName('footer'));
</script>
</head>
<body>
<div class="demo"><h1>lalala</h1><p>Hello</p></div>
<div class="footer"><p>hello</p><p>world</p></div>
</body>
</html>
I also tried
document.head.appendChild(script2);
which works and
document.body.appendChild(script2);
which doesn't work!
the problem is, document.body is not defined yet, it hasn't even started loading when the javascript is interpreted
There are a couple of problems with this.
You first need to make sure that you are running the javascript at the correct time. In your code, you are running the JS before the body tag is read. Instead place the <script> before the closing </body> tag.
Also, the insertBefore() function takes newNode and referenceNode as parameters. document.getElementsByTagName('footer') returns a list of elements. Instead, change it to document.getElementsByTagName('footer')[0] to retrun the 1st element in the list
Ok, I found it. This is the correct. I put it inside document.ready as Jaromanda X suggested and I add ('footer')[0] as Jackson suggested:
$( document ).ready(function() {
var script2 = document.createElement('script');
script2.text="alert('ΟΚ')";
document.body.insertBefore( script2, document.getElementsByClassName('footer')[0]);
});
Related
I have small snippet that is inside iframe and generates script html tag and appends it to the window.top.document.head.
Now I want to know how do I check from within potato.js from which iframe it was generated from once it is already loaded?
<!DOCTYPE html>
<html lang="en">
<head>
</head>
<body>
<iframe>
<!DOCTYPE html>
<html>
<head>
</head>
<body>
<script>
(function() {
var s = document.createElement('script');
s.setAttribute('type','text/javascript');
s.setAttribute('src','https://test.com/potato.js');
window.top.document.head.appendChild(s);
})();
</script>
</body>
</html>
</iframe>
</body>
</html>
Edit: I can not change this code inside the iframe
That information isn't stored automatically.
The only way I can think of would be to add an expando-prop to the script with a reference to the current window (i.e. the frame's window)…
s.sourceWindow = window;
… then read that from within potato.js …
const sourceWindow = document.currentScript.sourceWindow;
… and then loop over all the frames (window.frames) looking for a match.
Since you are using window.top and not window.parent you might need to be recursive there.
I know that this is a frequently asked question.
I have tried all the methods like using onload() for body tag,
placing the script after the DOM elements and using self invoking function.
Yet I get that my element is undefined.
P.S: document.getElementsByTagName('') replaced with document.getElementById('') works fine. Why is that? Please explain both of my doubts. Here is my simple code
<!DOCTYPE html>
<html>
<head>
<title></title>
</head>
<body onload="loadHandler()">
<p>Drag me!</p>
<script type="text/javascript">
function loadHandler() {
document.getElementsByTagName('p').setAttribute('draggable', true);
}
</script>
</body>
</html>
getElementsByTagName (as the name suggests) returns an array of elements. If you want the first one, take the first one.
.highlight{ color: red}
<!DOCTYPE html>
<html>
<head>
<title></title>
</head>
<body onload="loadHandler()">
<p>Drag me!</p>
<script type="text/javascript">
function loadHandler() {
var elem = document.getElementsByTagName('p')[0];
elem.setAttribute('draggable',true)
elem.classList.add('highlight');
}
</script>
</body>
</html>
As for why dragging is not working, perhaps the documentation might shed some light
By default, only text selections, images, and links can be dragged. For all others elements, the event ondragstart must be set for the drag and drop mechanism to work, as shown in this comprehensive example.
getElementsByTagName returns array of results, not just a single result like getElementById. Try to use getElementsByTagName('p')[0].
I have a code that works in JSFiddle but doesn't work when I save the HTML+JS locally and test it locally. I can't figure out what's wrong with the code. Here is my JSFiddle
http://jsfiddle.net/LLUAB/
And here is the actual code, not very long
<!doctype html>
<html>
<head>
<script type="text/javascript" language="Javascript">
function Composer(foobox) {
this.foobox = document.getElementById(foobox);
this.foobox.onkeydown = function(){window.alert("hello")};
}
var myComposer = new Composer("foo");
</script>
</head>
<body>
<textarea id="foo"></textarea>
</body>
</html>
Because in JSFiddle your script is placed inside window.onLoad event handler by default. While in your case getElementById() method is unable to find not yet loaded element.
Put all your script right before closing </body> tag and it will work:
<script type="text/javascript">
// ...
</script>
</body>
It works in Fiddle because of onLoad option specified here. The problem is that when new Composer line is fired, there's no such element in the DOM yet. Wrap this line in DOMReady handler - or move its invokation to the end of <body> element.
It's because your dom is not ready yet
function Composer(foobox) {
this.foobox = document.getElementById(foobox);
alert(this.foobox); --Prints null
this.foobox.onkeydown = function(){window.alert("hello")};
}
Working code here. http://jsfiddle.net/LLUAB/1/
This question already has answers here:
Why does jQuery or a DOM method such as getElementById not find the element?
(6 answers)
Closed 6 years ago.
Ok. I need fresh eyes because I'm still on this s***d problem for one hour!
Here is my simple HTML code (testssio.html) that include javascript script:
<!DOCTYPE html>
<html>
<head>
<script type="text/javascript">
var ssio = document.getElementById('ssio');
ssio.html = "it finally works!";
</script>
</head>
<body>
<div id="ssio"></div>
</body>
</html>
But it doesn't work! Using the debugger, I get:
Uncaught TypeError: Cannot set property 'html' of null /testssio/:6
Does anyone get it? I know it's not the correct place to look for debugging help, but I'll be crazy if I don't get it! So please, any help?
Tahnks in advance.
The reason for this is that scripts in the head load before the page is rendered. This means your content is not yet rendered and therefore not a part of document.
If you want to see this work, try moving your script below the element renders, like this:
<!DOCTYPE html>
<html>
<head>
</head>
<body>
<div id="ssio"></div>
<script type="text/javascript">
var ssio = document.getElementById('ssio');
ssio.innerHTML = "it finally works!";
</script>
</body>
</html>
A more standardized way of doing this is with events. Many people use jQuery but it can be done with plain js. This would mean changing your script like this:
<script type="text/javascript">
function WinLoad() {
var ssio = document.getElementById('ssio');
ssio.innerHTML = "It finally works!";
}
window.onload = WinLoad;
</script>
This way you can still leave it in the <head>.
Also, using .html is from jQuery. It is generally used as .html(content). If you want to use the plain javascript version use .innerHTML = content.
I mention jQuery so much because it is a highly used API. This quote is from their site:
jQuery is a fast and concise JavaScript Library that simplifies HTML document traversing, event handling, animating, and Ajax interactions for rapid web development. jQuery is designed to change the way that you write JavaScript.
Your code is running too early before the DOM is loaded and thus document.getElementById() doesn't find the element in the document yet.
You can either move your script tag down to right before the </body> tag or you can wait for the DOM to load before running your code with either the window onload event or a DOMReady event.
There are two errors here. First, you need to put the SCRIPT tag after the element. Second, it's not .html, but .innerHTML. So here is the corrected code:
<!DOCTYPE html>
<html>
<head>
</head>
<body>
<div id="ssio"></div>
<script type="text/javascript">
var ssio = document.getElementById('ssio');
ssio.innerHTML = "it finally works!";
</script>
</body>
</html>
you can use something like this
<!DOCTYPE html>
<html>
<head>
<script type="text/javascript">
document.onload= function(){
var ssio = document.getElementById('ssio');
ssio.html = "it finally works!";
}
</script>
</head>
<body>
<div id="ssio"></div>
I have been trying to use the document.getElementByID to pull information from an HTML file from an external JS file and it does not seem to be working. Does the document.getElementByID only work if it is inline with the HTML file or can it work properly on an external JS file? The JS file is called upon within the HTML document properly because other functions are working.
First off, make sure you're using document.getElementById("xxx"), not document.getElementByID("xxx") (note the difference in capitalization at the end). Your question refers to document.getElementByID("xxx") so that could be the problem right here.
Second, you must make sure that the function is executed AFTER the relevant DOM items have been parsed by the browser. If you are putting the document.getElementById in an external JS file that is loaded in the <head> section and is executed immediately after it loads, then the DOM will not yet be ready.
You have several options:
1) Place the external JS file <script> tags at the end of the body, right before the </body> tag. This will not only load/display your page faster, but will guarentee that the DOM is parsed before anything in that JS file can run.
<body>
Your HTML here
<script type="text/javascript" src="myscript.js"></script>
</body>
2) Since you have jQuery, put your immediately executed code inside of a $(document).ready(fn) block so that jQuery will hold back the execution until the DOM is ready. If you do it this way, then you can put your code anywhere (including in the <head> section if you want).
$(document).ready(function() {
// put your page initialization code here
});
3) Put your code anywhere you want, but don't have any of it execute immediately. Instead, put all your initialization code in an intialization function (let's call it myPageInit() that you call from:
$(document).ready(myPageInit);
4) Put your code anywhere you want, but don't have any of it execute immediately. Instead, put all your initialization code in an intialization function (let's call it myPageInit() that you call from a script right before the </body> tag with this:
<script type="text/javascript">myPageInit()</script>
Does the document.getElementByID only work if it is inline with the HTML file
No.
can it work properly on an external JS file?
Yes.
You're probably calling document.getElementById() before the DOM is ready.
My suggestion is to do this:
window.onload = function () {
// document.getElementById() code here
}
Then your document.getElementById() would not execute until every element on the page has fully loaded.
If you put the script in the <head> then the body hasn't loaded yet and so the elements aren't there.
Either defer the script by using jQuery's functions, or put the script at the end of the body.
window.onload = function() {
document.getElementById("demo").innerHTML = "My First JavaScript";
}
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>js in ts</title>
<script src="app.js"></script>
</head>
<body>
<h2>JavaScript in Body</h2>
<p id="demo"></p>
</body>
</html>