Hi I am learning to build Chrome Extensions and am very new to this field. I am working on a very basic extension here and even before I have started on the main task, I am stuck in my demo code. I simply wish to print "hello" or any message in my paragraph tag when I click my extension.
Here is the HTML code:
<!DOCTYPE html>
<html>
<head>
<title>hi</title>
<style>
p
{
color:red;
font-size:20px;
}
</style>
<script src="getMSG.js"></script>
</head>
<body>
<p id='content'></p>
</body>
</html>
And here is the code for getMSG.js:
document.getElementById('content').innerHTML = 'Hello';
My extentsion was working just fine when I simply wrote "Hello World" in my HTML code. But now when I do this I get no output at all. Please can someone help with this? Thanks in advance :)
To access the properties of a DOM element you need to do that operation when the window load:
// Using pure JavaScript
window.onload = function() {
document.getElementById('content').innerHTML = 'Hello';
}
I was tested your code and it doesn't work, i think the content page wasn't loaded completely,
So it's preferred to use jQuery accompany this code in your "getMSG.js":
$(document).ready(function () {
document.getElementById('content').innerHTML = 'Hello';
});
Works fine for me.
Related
<!DOCTYPE html>
<html>
<head>
<title>LearnJS</title>
</head>
<body>
<script>
console.log('hello World\nThis is me');
alert("This is an \nalert.");
</script>
</body>
</html>
I have tried this code and run in TORCH borwser... The only output shown is alert But it doesn't display output of console.log...
What is the possible solution...
I have use
document.write('hello World\nThis is me');
But this code doesn't feed new line so i was supposed to use console.log...
It is working fine here :). Run Code Snippet
<!DOCTYPE html>
<html>
<head>
<title>LearnJS</title>
</head>
<body>
<script>
console.log('hello World\nThis is me on console');
alert("This is an \nalert.");
document.write("This is an document.write.");
</script>
</body>
</html>
Note:
developers use console.log() for logging useful information on browser console
document.write() modifies what user sees in the browser by adding additional content to DOM.
alert()'s are used to alert end users who access the web page on browser.
N.B If you're in confusion about How stackoverflow.com shows console.log() on a browser div. Then see here https://stackoverflow.com/a/20256785/1138192 it is kind of overriding the default behavior of console.log() to show the messages on browser div. Hope this helps :)
console.log() only displays in the developer console of the browser. It does not display on the web page itself.
Your code is not feeding a new line because \n only shows in the source code not on the page. To display a new line in HTML on the page you need to use a <br> tag or use other form of spacing.
So, instead of:
document.write('hello World\nThis is me');
You could use:
document.write('hello World<br>This is me');
However, rather than using document.write(), you may prefer to write to a specific element in the page. Below I give an element an id of data and then use the JavaScript code to write to this element.
<!DOCTYPE html>
<html>
<body>
<div id="data">You can put text here or leave it blank. It will be replaced.</div>
<script>
document.getElementById("data").innerHTML = "Hello world<br>This is me";
</script>
</body>
</html>
Notice also, I need to place the document.getElementByID("data") script after the div is created. If I place it before it will not be able to find it. The script code is therefore placed at the end of the <body> section. There are better ways to do this (such as placing JavaScript code in an external file and using defer), but for your purposes this should work quite well.
my very simple html code, actually my javascript code is not working, here is my code:
<!DOCTYPE html>
<html>
<head>
<script>
function write(){
document.getElementById("div1").innerHTML = "hello world";
}
</script>
</head>
<body>
<div id="div1" onclick="write()">hello</div>
</body>
</html>
i want to change the <div> content to "hello world". but when i try to do it, when i click the <div> element, its content is erased and it gives me a blank page. what am i doing wrong? any help would be appreciated.
That happens because 'write' is already defined as a method from the document object. You need to change the name of the method to something else.
What i want to do is simple. When i click the image, i want some message to appear.
Afterwards, when i click it again i want it to disappear. I have problems iplementing it
due to my lack of jQuery knowledge. I would appreciate some help with the following code, as well as some other implementations. I know i can do something with class="hidden" and have jQuery add/remove it but oh well.
This is what i'm trying to work with.
<!DOCTYPE html>
<html>
<head>
<script>
function greet(){
a = document.getElementById('here');
if (a.trim().length==0){
a.innerHTML = 'message!';
}
else{
a.innerHTML = '';
}
</script>
</head>
<body>
<img src="http://www.clker.com/cliparts/K/9/M/I/M/8/on-button-small-th.png" alt="alt" onclick="greet()"/>
<p id='here'></p>
</body>
</html>
EDIT: seems like i should use a.value, but i must be doing something else wrong too.
If you are using jQuery it is very simple; just use this as your JavaScript (don't forget to link the jQuery main library - I like the Google CDN for that). Just use the toggle function:
function greet() {
$('#here').toggle();
}
Also it is better to register the onClick through jQuery rather than your html (for examplesee this SO question). So that would be like this for the whole page instead :
<!DOCTYPE html>
<html>
<head>
<script src="//ajax.googleapis.com/ajax/libs/jquery/1.11.0/jquery.min.js"></script>
<script>
$( document).ready(function() {
$("#greet").click(
function () {
$('#here').toggle();
}
);
$("#here").hide();
}
</script>
</head>
<body>
<img id="greet" src="http://www.clker.com/cliparts/K/9/M/I/M/8/on-button-small-th.png" alt="alt"/>
<p id='here'><!--MESSAGE SHOULD BE HERE--></p>
</body>
</html>
Working example in jsFiddle.
EDIT:[Honestly this works fine you can read my edit comment below.]
So I am very new to JavaScript. This book I have tells me that I can write the script code in another file that has a .js extension. What it doesn't tell me is what should be in that .js extension.
<html>
<head>
<title>Title of Document</title>
<script src="path/to/file/fileName.js"></script>
</head>
<body>
The content of
your page goes here.
</body>
</html>
Lets say I wanted to make an alert message in the java script file. Inside the "fileName.js" would all I write be:
alert("This is an alert box");
and then save it and call it quits? Cause that is what I have so far and nothing doing.
EDIT:
Ok I want to add this in for anyone in trouble like I was. Turns out, this works perfectly. The comments below are a great help for further information. But the thing I did not realize was that on my Mac I needed to start the path to file at /Users. I feel dumb but at least I figured it out. Thanks all for your help.
Use " instead of ”:
<script src="path/to/file/fileName.js"></script>
^ ^
Generally your js files will have objects and Methods that are called/used from you main page.
So you html wiil look like :
<html>
<head>
<title>Title of Document</title>
<script src="path/to/file/fileName.js"></script>
</head>
<body onload="showAlert();">
The content of
your page goes here.
</body>
</html>
and you js will look like:
function showAlert(){
alert("This is an alert box");
}
Look into events and listeners. For example, if you want the alert to come up when the page loads, your html file would have:
<body onload="functionName()">
</body>
And you javascript file would have:
function functionName() {
alert("alert message");
}
Usually you would write your Javascript code as a series of functions that you can call whenever you need. So yes, you can write a single statement the way you did but most times its functions.
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>