JavaScript Introduction


JavaScript Tutorial for beginners and professionals is a solution of client side dynamic pages. JavaScript is an object-based scripting language that is lightweight and cross-platform programming language.

JavaScript is not compiled but translated.The JavaScript Translator (embedded in browser) is responsible to translate the JavaScript code.

  • JavaScript is:
    • JavaScript is a lightweight, interpreted programming language
    • Designed for creating network-centric applications
    • Complementary to and integrated with Java
    • Complementary to and integrated with HTML
    • Open and cross-platform

Advantages of JavaScript

The merits of using JavaScript are:
  • Less server interaction: You can validate user input before sending the page off to the server. This saves server traffic, which means less load on your server.
  • Immediate feedback to the visitors: They don't have to wait for a page reload to see if they have forgotten to enter something.
  • Increased interactivity: You can create interfaces that react when the user hovers over them with a mouse or activates them via the keyboard.
  • Richer interfaces: You can use JavaScript to include such items as drag-and-drop components and sliders to give a Rich Interface to your site visitors.

Where JavaScript is used

It is used to create interactive websites. It is mainly used for:

  • Client-side validation
  • Dynamic drop-down menus
  • Displaying data and time
  • Displaying popup windows and dialog boxes (like alert dialog box, confirm dialog box and prompt dialog box)
  • Displaying clocks etc.

Limitations with JavaScript

We can not treat JavaScript as a full fledged programming language. It lacks the following important features:

  • Client-side JavaScript does not allow the reading or writing of files. This has been kept for security reason.
  • JavaScript can not be used for Networking applications because there is no such support available.
  • JavaScript doesn't have any multithreading or multiprocess capabilities.

JavaScript Development Tools

One of JavaScript's strengths is that expensive development tools are not usually required. You can start with a simple text editor such as Notepad.

Since it is an interpreted language inside the context of a web browser, you don't even need to buy a compiler.

To make our life simpler, various vendors have come up with very nice JavaScript editing tools. Few of them are listed here:

  • Microsoft FrontPage: Microsoft has developed a popular HTML editor called FrontPage. FrontPage also provides web developers with a number of JavaScript tools to assist in the creation of an interactive web site.
  • Macromedia Dreamweaver MX: Macromedia Dreamweaver MX is a very popular HTML and JavaScript editor in the professional web development crowd. It provides several handy prebuilt JavaScript components, integrates well with databases, and conforms to new standards such as XHTML and XML.
  • Macromedia HomeSite 5: This provided a well-liked HTML and JavaScript editor, which will manage their personal web site just fine.

JavaScript Can Change HTML Elements

One of many HTML methods is document.getElementById().

This example changes the content (innerHTML) of an HTML element identified with id="view":

document.getElementById("view").innerHTML = "Hello JavaScript";

JavaScript Can Change HTML Styles (CSS)

Changing the style of an HTML element, is a variant of changing an HTML attribute

document.getElementById("demo").style.fontSize = "25px";

JavaScript Can Validate Data

JavaScript is often used to validate input

function myFunction() {
    var x;
    var text = "Input OK";

    //Get the value of input field with id="numb"
    x = document.getElementById("numb").value;

    // If x is Not a Number, or x is less than one, or x is grather than 10 then
    if (isNaN(x) || x < 1 || x > 10) {
        text = "Not valid";
    }
    document.getElementById("demo").innerHTML = text;
}

Please input a number between 1 and 10


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