Javascript Tutorials
JavaScript is one of 3 languages all web developers must learn:1. HTML to define the content of web pages
2. CSS to specify the layout of web pages
3. JavaScript to program the behavior of web pages
The HTML DOM (the Document Object Model) is the official W3C standard for accessing HTML elements.
JavaScript can manipulate the DOM (change HTML contents).
The following example changes the content (innerHTML) of an HTML element identified with id="demo":
Example
document.getElementById("demo").innerHTML = "Hello JavaScript";
The method document.getElementById() is one of many methods in the HTML DOM.
You can use JavaScript to:
- Change HTML elements
- Delete HTML elements
- Create new HTML elements
- Copy and clone HTML elements
- And much more ...
My First JavaScript
JavaScript can change the content of an HTML element:
This is a demonstration.My First JavaScript
JavaScript can change the content of an HTML element:
Hello JavaScript!In HTML, JavaScripts must be inserted between tags.JavaScripts can be put in the and in the section of an HTML page.The tells where the JavaScript starts and ends.
The lines between contain the JavaScript
code:
JavaScript is the default scripting language
in all modern browsers, and in HTML5.
JavaScript in
In this example, a JavaScript function is placed in the section
of an HTML page.
The function is invoked (called) when a button is clicked:
Example
<!DOCTYPE html><html><head> <script>
function myFunction() {
document.getElementById("demo").innerHTML = "Paragraph changed.";
} </script> </head>
<body>
<h1>My Web Page</h1>
<p id="demo">A Paragraph</p>
<button type="button" onclick="myFunction()">Try it</button>
</body>
N/B
It is a good idea to place scripts at the bottom of the element.
This improves page load, because HTML loading is not blocked by scripts loading.
This improves page load, because HTML loading is not blocked by scripts loading.
External JavaScripts
Scripts can also be placed in external files.
External scripts are practical when the same code is used
in many different
web pages.
JavaScript files have the file extension .js.
To use an external script, put the name of the script file in the source (src) attribute of the
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