JavaScript is program code that you embed into the HTML5 code. The web server sends the JavaScript program code to your site visitors’ web browsers, which in turn detect and run the JavaScript code. The JavaScript code can alter features of the web page that the HTML5 and CSS3 code produce.
Changing web page content
In your HTML5 code, you no doubt will have lots of text that appears in separate sections of your web page. For example, you may have a sidebar element that lists the day’s news events related to your website topic, or you may have a header element that displays the current time and temperature for your city.All that is great, but you need a way for that information to change dynamically, each time your site visitors load the web page. This is where JavaScript comes in.
JavaScript code allows you to alter the text that appears on your web page “on the fly,” without requiring your site visitors to reload the web page. You can create JavaScript code that retrieves updated news articles even as your site visitors are viewing your web pages. The information will change right before their eyes — like magic!
Changing web page styles
You add CSS3 styles to your web pages to apply styles to text and elements, or to place elements in specific locations on the web page. The CSS3 code you create is placed inline in the HTML5 elements, internally in the head element of the web page, or as an external style sheet.JavaScript code allows you to dynamically alter any style or position that you define for an HTML5 element in your CSS3 code. That’s right — you can use JavaScript to turn blue backgrounds yellow, orange text green, or even move an entire section of text from one side of the web page to another! That’s a lot of control to have at your fingertips.
One of the coolest features of JavaScript is the ability to dynamically make HTML5 elements appear out of nowhere! Each HTML5 element supports the display style property, which you use to determine how or if the element appears on the web page.
display style property for any element on the web page to make it appear as needed or disappear when not needed. That gives you the ability to dramatically alter the layout of a web page at any time while your site visitor is interacting with the web page. This helps hide sections that may be distracting to site visitors at times, then make them appear when the site visitor needs to interact with them.