DHTML JavaScript - GeeksforGeeks

03 Dec, 2018
DHTML stands for Dynamic HTML. Dynamic means that the content of the web page can be customized or changed according to user inputs i.e. a page that is interactive with the user. In earlier times, HTML was used to create a static page. It only defined the structure of the content that was displayed on the page. With the help of CSS, we can beautify the HTML page by changing various properties like text size, background color etc. The HTML and CSS could manage to navigate between static pages but couldn’t do anything else. If 1000 users view a page that had their information for eg. Admit card then there was a problem because 1000 static pages for this application build to work. As the number of users increase, the problem also increases and at some point it becomes impossible to handle this problem.
To overcome this problem, DHTML came into existence. DHTML included JavaScript along with HTML and CSS to make the page dynamic. This combo made the web pages dynamic and eliminated this problem of creating static page for each user. To integrate JavaScript into HTML, a Document Object Model(DOM) is made for the HTML document. In DOM, the document is represented as nodes and objects which are accessed by different languages like JavaScript to manipulate the document.
HTML document include JavaScript:: The JavaScript document is included in our html page using the html tag. <src> tag is used to specify the source of external JavaScript file.Following are some of the tasks that can be performed with JavaScript:
Performing html tasks
Performing CSS tasks
Handling events
Validating inputs
Example 1: Example to understand how to use JavaScript in DHTML.
<html>    <head>        <title>DOM programming</title>    </head>          <body>        <h1>GeeksforGeeks</h1>        <p id = "geeks">Hello Geeks!</p>        <script style = "text/javascript">        document.getElementById("geeks").innerHTML =               "A computer science portal for geeks";        </script>    </body></html>                    
Output:Explanation: In the above example, change the text of paragraph which using id. Document is an object of html that is displayed in the current window or object of DOM. The getElementById(id) gives the element id. The innerHTML defines the content within the id element. The id attribute is used to change HTML document and its property. Paragraph content changed by document id. For example: document.getElementById(“geeks”).style.color = “blue”; It is used to set the paragraph color using id of elements.
Example 2: Creating an alert on click of a button.
<html>    <head>        <title>Create an alert</title>    </head>          <body>        <h1 id = "para1">GeeksforGeeks</h1>        <input type = "Submit" onclick = "Click()"/>        <script style = "text/javascript">            function Click() {                document.getElementById("para1").style.color = "#009900";                window.alert("Color changed to green");            }        </script>    </body></html>                    
Output:Explanation: In this example, creating a function that will be invoked on click of a button and it changes the color of text and display the alert on the screen. window is an object of current window whose inbuilt method alert() is invoked in Click() function.
Example 3: Validate input data using JavaScript.
<html>    <head>        <title>Validate input data</title>    </head>          <body>        <p>Enter graduation percentage:</p>        <input id="perc">        <button type="button" onclick="Validate()">Submit</button>        <p id="demo"></p>        <script>            function Validate() {                var x, text;                x = document.getElementById("perc").value;                if (isNaN(x) || x < 60) {                    window.alert("Not selected in GeeksforGeeks");                } else {                document.getElementById("demo").innerHTML =                               "Selected: Welcome to GeeksforGeeks";                document.getElementById("demo").style.color = "#009900";                }            }        </script>    </body></html>                    
Output:Explanation: In this example, make a validate() function which ensures the user is illegible or not. If user enters > 60 then selected otherwise not selected.
Attention reader! Don’t stop learning now. Get hold of all the important HTML concepts with the Web Design for Beginners | HTML  course.
HTML-Misc
javascript-basics
Picked
HTML
Web Technologies
HTML
Writing code in comment?
Please use ide.geeksforgeeks.org,
generate link and share the link here.
Comments
Old Comments
Top 10 Projects For Beginners To Practice HTML and CSS Skills
How to insert spaces/tabs in text using HTML/CSS?
How to set the default value for an HTML <select> element ?
How to update Node.js and NPM to next version ?
How to set input type date in dd-mm-yyyy format using HTML ?
Roadmap to Become a Web Developer in 2022
Installation of Node.js on Linux
Top 10 Projects For Beginners To Practice HTML and CSS Skills
How to fetch data from an API in ReactJS ?
How to insert spaces/tabs in text using HTML/CSS?