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14.5 DOM HTML

The HTML DOM allows JavaScript to change the content of HTML elements.

Changing HTML Content

The easiest way to modify the content of an HTML element is by using the innerHTML property.
To change the content of an HTML element, use this syntax:

document.getElementById(id).innerHTML = new HTML

This example changes the content of a <p> element:

Example 1: JS Changing HTML Content part 1

<html>
<body>

<p id="p1">Hello World!</p>

<script>
document.getElementById("p1").innerHTML = "New text!";
</script>

</body>
</html>

Example explained:
- The HTML document above contains a <p> element with id="p1"
- We use the HTML DOM to get the element with id="p1"
- A JavaScript changes the content (innerHTML) of that element to "New text!"
This example changes the content of an <h1> element:

Example 2: JS Changing HTML Content part 2

<!DOCTYPE html>
<html>
<body>

<h1 id="id01">Old Heading</h1>

<script>
const element = document.getElementById("id01");
element.innerHTML = "New Heading";
</script>

</body>
</html>

Example explained:
- The HTML document above contains an <h1> element with id="id01"
- We use the HTML DOM to get the element with id="id01"
- A JavaScript changes the content (innerHTML) of that element to "New Heading"

Changing the Value of an Attribute

To change the value of an HTML attribute, use this syntax:

document.getElementById(id).attribute = new value

This example changes the value of the src attribute of an <img> element:

Example 3: JS HTML DOM - Changing the Value of an Attribute

<!DOCTYPE html>
<html>
<body>

<img id="myImage" src="smiley.gif">

<script>
document.getElementById("myImage").src = "landscape.jpg";
</script>

</body>
</html>

Example explained:
- The HTML document above contains an <img> element with id="myImage"
- We use the HTML DOM to get the element with id="myImage"
- A JavaScript changes the src attribute of that element from "smiley.gif" to "landscape.jpg"

Dynamic HTML content

JavaScript can create dynamic HTML content:
Date : Fri Nov 24 2023 15:43:58 GMT+0100 (Central European Standard Time)

Example 4: JS HTML DOM - Dynamic HTML content

<!DOCTYPE html>
<html>
<body>

<script>
document.getElementById("demo").innerHTML = "Date : " + Date(); </script>

</body>
</html>

document.write()

In JavaScript, document.write() can be used to write directly to the HTML output stream:

Example 5: JS HTML DOM - document.write()

<!DOCTYPE html>
<html>
<body>

<p>Bla bla bla</p>

<script>
document.write(Date());
</script>

<p>Bla bla bla</p>

</body>
</html>

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Module 14. JS HTML DOM

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Example files created in this module:
HTML DOM Methods JS HTML DOM - Finding HTML Element by Id JS HTML DOM - Finding HTML Elements by Tag Name part 1 JS HTML DOM - Finding HTML Elements by Tag Name part 2 JS HTML DOM - Finding HTML Elements by Class Name JS HTML DOM - Finding HTML Elements by CSS Selectors JS HTML DOM - Finding HTML Elements by HTML document.forms JS Changing HTML Content part 1 JS Changing HTML Content part 2 JS HTML DOM - Changing the Value of an Attribute JS HTML DOM - Dynamic HTML content JS HTML DOM - document.write() JS Validation - HTML Form Example part 1 JS Validation - HTML Form Example part 2 JS HTML DOM - Changing the HTML style JS HTML DOM - Changing the HTML style Using Events My first JS animation part 1 My first JS animation part 2 JS HTML Events - The onclick Attribute part 1 JS HTML Events - The onclick Attribute part 2 JS HTML Events - The onclick Attribute part 3 JS HTML Events - The onclick Attribute part 4 JS HTML Events - The onload Attribute JS addEventListener() part 1 JS addEventListener() part 2 JS addEventListener() part 3 JS addEventListener() part 4 JS addEventListener() part 5 JS addEventListener() part 6 JS addEventListener() part 7 JS addEventListener() part 8 JS removeEventListener() JS HTML Child Nodes and Node Values part 1 JS HTML Child Nodes and Node Values part 2 JS HTML Child Nodes and Node Values part 3 JS HTMLDOM - DOM Root Nodes part 1 JS HTMLDOM - DOM Root Nodes part 2 JS HTMLDOM - The nodeName Property JS HTMLDOM - The nodeType Property JS HTML DOM - Creating New HTML Elements (Nodes) JS HTML DOM - Creating new HTML Elements - insertBefore() JS HTML DOM - Removing Existing HTML Elements JS HTML DOM - Remove Child Element JS HTML DOM - Replacing an HTML Elements JS HTML DOM Collections JS HTML DOM Collections - HTMLCollection Length par 1 JS HTML DOM Collections - HTMLCollection Length part 2 JS HTML DOM - DOM Node Lists JS HTML DOM - DOM Node List Length part 1 JS HTML DOM - DOM Node List Length part 2