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JavaScript Introduction
JavaScript is the world's most popular programming language. It is the language for HTML and the web, for servers, PCs, laptops, tablets, smart phones, and more.

JavaScript is a Scripting Language

A scripting language is a lightweight programming language.

JavaScript is programming code that can be inserted into HTML pages.

JavaScript inserted into HTML pages, can be executed by all modern web browsers.

JavaScript is easy to learn.


What You Will Learn

Below is a taste of what you will learn in this tutorial.


JavaScript: Writing Into HTML Output

Example

document.write("<h1>This is a heading</h1>");
document.write("<p>This is a paragraph</p>");

Try it yourself »

lamp You can only use document.write in the HTML output. If you use it after the document has loaded, the whole document will be overwritten.


JavaScript: Reacting to Events

Example

<button type="button" onclick="alert('Welcome!')">Click Me!</button>

Try it yourself »

The alert() function is not much used in JavaScript, but it is often quite handy for trying out code.

The onclick event is only one of the many HTML events you will learn about in this tutorial.


JavaScript: Changing HTML Content

Using JavaScript to manipulate the content of HTML elements is a very powerful functionality.

Example

x=document.getElementById("demo")  //Find the element
x.innerHTML="Hello JavaScript";    //Change the content

Try it yourself »

You will often see document.getElementByID("some id"). This is defined in the HTML DOM.

The DOM (Document Object Model) is the official W3C standard for accessing HTML elements.

You will find several chapters about the HTML DOM in this tutorial.


JavaScript: Changing HTML Images

This example dynamically changes the source (src) attribute of an HTML <image> element:

The Light bulb

Click the light bulb to turn on/off the light


Try it yourself »

JavaScript can change most of the attributes of any HTML element, not only images.


JavaScript: Changing HTML Styles

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

Example

x=document.getElementById("demo")  //Find the element
x.style.color="#ff0000";           //Change the style

Try it yourself »


JavaScript: Validate Input

JavaScript is commonly used to validate input.

Example

if isNaN(x) {alert("Not Numeric")};

Try it yourself »


Did You Know?

lamp JavaScript and Java are two completely different languages, in both concept and design.
Java (invented by Sun) is a more complex programming language in the same category as C.

ECMA-262 is the official name of the JavaScript standard.

JavaScript was invented by Brendan Eich. It appeared in Netscape (a no longer existing browser) in 1995, and has been adopted by ECMA (a standard association) since 1997.

Parameters


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Examples


Reference

See Also


On the forum about JavaScript Introduction

[@EOF@]...

Product: . Written by alembagheri tahmas 07/12/13 at 13:37:32

Hi there,I am trying to use an external MySQL DB in dataease. I have successfully create the ODBC link and added the DB to dataease. I can also access the DB from dataease. Now, just for testing purposes, I am trying to create a simple report b...

Product: DataEase for Windows 7.x. Written by George Washington 11/04/14 at 08:26:17

no se pude exportar ahora archivos a pdf, ni a excel o otros cosa mala. en verdad creo que hace faltaen las versiones anteriores me funcionaba mas o menos bien.&nbsp;le hace falta a los aplicativos que se desarrollan en Dataeasegr...

Product: DataEase 8 Reporter. Written by eduardo paez 02/05/14 at 14:40:11

Thanks. Anyway I'm trying to use this fuction but it seems to me that it doesn't work on 8.2. I tried also in a DQL.There's something wrong?<img src="data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAA9IAAAJ3CAYAAAB4NWk3AAAAAXNSR0IArs4...

Product: . Written by Marco Marchesi 15/02/16 at 14:50:46

[@EOF@]...

Product: Dataease [{8}]FIVE. Written by Chamil Rajindra 21/02/19 at 10:17:46

Thanks for the very good explanation!AS...

Product: . Written by afonso santos 28/10/19 at 00:50:14

I am pleased to see that the migration from Dos 4.53 is then sa 5.5 works. A really useful thing would be a compiler of SQL languages. Will you get there?Original Text:Mi compiaccio a vedere che la migrazione da Dos 4.53 è poi sa 5.5 funzio...

Product: . Written by Grossi Gioacchino 18/11/19 at 14:33:44

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