Change document html javascript

JavaScript HTML DOM Document

The HTML DOM document object is the owner of all other objects in your web page.

The HTML DOM Document Object

The document object represents your web page.

If you want to access any element in an HTML page, you always start with accessing the document object.

Below are some examples of how you can use the document object to access and manipulate HTML.

Finding HTML Elements

Method	Description
document.getElementById(id)	Find an element by element id
document.getElementsByTagName(name)	Find elements by tag name
document.getElementsByClassName(name)	Find elements by class name

Changing HTML Elements

Property	Description
element.innerHTML = new html content	Change the inner HTML of an element
element.attribute = new value	Change the attribute value of an HTML element
element.style.property = new style	Change the style of an HTML element
Method	Description
element.setAttribute(attribute, value)	Change the attribute value of an HTML element

Adding and Deleting Elements

Method	Description
document.createElement(element)	Create an HTML element
document.removeChild(element)	Remove an HTML element
document.appendChild(element)	Add an HTML element
document.replaceChild(new, old)	Replace an HTML element
document.write(text)	Write into the HTML output stream

Adding Events Handlers

Method	Description
document.getElementById(id).onclick = function()code>	Adding event handler code to an onclick event

Finding HTML Objects

The first HTML DOM Level 1 (1998), defined 11 HTML objects, object collections, and properties. These are still valid in HTML5.

Later, in HTML DOM Level 3, more objects, collections, and properties were added.

Property	Description	DOM
document.anchors	Returns all elements that have a name attribute	1
document.applets	Deprecated	1
document.baseURI	Returns the absolute base URI of the document	3
document.body	Returns the element	1
document.cookie	Returns the document’s cookie	1
document.doctype	Returns the document’s doctype	3
document.documentElement	Returns the element	3
document.documentMode	Returns the mode used by the browser	3
document.documentURI	Returns the URI of the document	3
document.domain	Returns the domain name of the document server	1
document.domConfig	Obsolete.	3
document.embeds	Returns all elements	3
document.forms	Returns all elements	1
document.head	Returns the element	3
document.images	Returns all elements	1
document.implementation	Returns the DOM implementation	3
document.inputEncoding	Returns the document’s encoding (character set)	3
document.lastModified	Returns the date and time the document was updated	3
document.links	Returns all and elements that have a href attribute	1
document.readyState	Returns the (loading) status of the document	3
document.referrer	Returns the URI of the referrer (the linking document)	1
document.scripts	Returns all elements	3
document.strictErrorChecking	Returns if error checking is enforced	3
document.title	Returns the element	1
document.URL	Returns the complete URL of the document	1

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JavaScript HTML DOM — Changing 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:

This example changes the content of a

element:

Example

• The HTML document above contains a

  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 element:

Example

• The HTML document above contains an 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:

This example changes the value of the src attribute of an element:

Example

• The HTML document above contains an 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:

Example

document.write()

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

Example

Never use document.write() after the document is loaded. It will overwrite the document.

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How to Change HTML with JavaScript

By using JavaScript, you can change any part of an HTML document in response to input from the person browsing the page. Before you get started, take a look at a couple of concepts. The first is a method called getElementById .

A method is an action that’s done to or by an object in a JavaScript program.

Fetching elements with getElementById

getElementById is probably the easiest and most commonly used way for JavaScript programmers to work directly with HTML. Its purpose is to locate an individual element in a document so that you can change it, delete it, or add some­thing to it.

Another word for locating an element is selecting an element.

To use getElementById , first make sure that the element you want to select has an id attribute. Then just use the following formula to locate that element:

document.getElementById("id‐value")

For example, to select an element with an id value of myName , you can use this code:

document.getElementById("myName")

Getting what’s inside an element with innerHTML

When you have an element, the next logical thing to do is to make a change to it.

innerHTML is a property of every element. It tells you what’s between the starting and ending tags of the element, and it also lets you set the contents of the element.

A property describes an aspect of an object. It’s something that an object has as opposed to something that an object does.

For example, say that you have an element like the following:

You can select the paragraph and then change the value of its innerHTML with the following command:

document.getElementById("myParagraph").innerHTML = "This is your paragraph!";

Trying it out: Changing a list

Now that you know a little about getElementById and innerHTML , take a look at an HTML home page. You’ll add a button and JavaScript code to your home page to let you change your list of favorite things with the click of a button.

Add a button below the list with the following HTML:

var item1; var item2; var item3;

document.getElementById("changeList").onclick = newList;

The updateList function finds each of the list items using their id attribute values. It then uses a method called innerHTML to change the value that’s between the starting and ending tags of the list item to the values that the user entered into the prompt. After the updateList function gets run, the values of the three list items should change to the new values entered by the user. When you’re finished, your code in the JavaScript pane should match the following code. Check it very carefully before moving on to make sure you don’t have any syntax errors.

var item1; var item2; var item3; document.getElementById(«changeList»).onclick = newList; function newList() < item1 = prompt("Enter a new first thing: "); item2 = prompt("Enter a new second thing: "); item3 = prompt("Enter a new third thing: "); updateList(); >function updateList()

If you did everything correctly, you should now be able to click the button, enter new text into each of the three prompt windows, and then see the new items instead of the three original list items, as shown here.

About This Article

This article is from the book:

About the book authors:

Chris Minnick and Eva Holland are experienced web developers, tech trainers, and coauthors of Coding with JavaScript For Dummies. Together they founded WatzThis?, a company focused on training and course development.

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