Introduction to JavaScript

JavascriptIntroduction

JavaScript is the most popular scripting language on the Internet, which can be used in HTML and the Web, and is more widely used in servers, PCs, laptops, tablets and smartphones.

JavaScript is a scripting language

JavaScript is a lightweight programming language.

JavaScript is a programmatic code that can be inserted into an HTML page.

When JavaScript is inserted into an HTML page, it can be performed by all modern browsers.

JavaScript is easy to learn.

What you will learn

Here are the main things you will learn in this tutorial.

JavaScript: Write directly to the HTML output stream instance document.write ("document.write ("<p> This is a paragraph. </p> ");
Try it»

	You can only use document.write in HTML output. If you use this method after the document is loaded, the entire document is overwritten.

JavaScript: An example of a response to an event <button type= "button" onclick= "alert (' Welcome! ')" > I!</button>.
Try it»

The alert () function is not commonly used in JavaScript, but it is very handy for code testing.

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

JavaScript: changing HTML content

Using JavaScript to work with HTML content is a powerful feature.

Instance X=document.getelementbyid ("demo")//Find element
X.innerhtml= "Hello JavaScript"; Change Content
Try it»

You will often see document.getElementById ("some ID"). This method is defined in the HTML DOM.

The DOM (Document Object MOdel) (Document Object model) is the official standard for accessing HTML elements.

You'll learn more about HTML DOM in several chapters of this tutorial.

JavaScript: changing HTML images

This meeting dynamically changes the source of HTML <image> (SRC):

Light the light bulb.

Tap the light bulb to turn the lamp on or off

Try it»

JavaScript can change most attributes of any HTML element, not just pictures.

JavaScript: changing HTML styles

Changing the style of HTML elements is a variant of changing HTML attributes.

Instance X=document.getelementbyid ("demo")//Find element
X.style.color= "#ff0000"; Change Style
Try it»

JavaScript: Validating input

JavaScript is often used to validate user input.

instance if IsNaN (x) {alert ("not a Number")};
Try it»

Did you know that?

	JavaScript and Java are two completely different languages, both conceptually and in design. Java (invented by Sun) is a more complex programming language. ECMA-262 is the official name of the JavaScript standard. JavaScript was invented by Brendan Eich. It appeared in Netscape in 1995 (the browser has stopped updating) and was adopted by the ECMA (a standard association) in 1997.

Introduction to JavaScript