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Lesson 2 jQuery Basics


The basic function of jQuery is to select some HTML elements from a webpage and perform some actions on them. This will update the content of the webp page.

The jQuery syntax is as follows:

 $(selector).action()
Explanation
A $ sign to define/access jQuery
A (selector) to "query (or find)" HTML elements
A jQuery action() to be performed on the elements. 

action is actually a jQuery method. There are numerous jQuery methods. The following examples uses the hide method to hide selected elements.

For Examples:

$(this).hide() - hides the current element.

$("p").hide() - hides all <p> elements.

$(".abc").hide() - hides all elements with class="abc".

$("#abc").hide() - hides the element with id="abc".

You need to place the jQuery JavaScript in the <head> sction of the webpage, as follows:

<!DOCTYPE html>
<html>
<head>
<script>
$(document).ready(function(){
    // jQuery code......
});
</script>
</head>

An alternative method is to create a jQuery JavaScript file and link it to the web page. For example, you have created a jQuery JavaScript file jqry.js. Link this file using the syntax as follows and place it within the <body> section of the webpage:

<script src="jquery/jqry.js"></script>

Example 2.1

In this example, we use the jquery 'hide' method to hide the h1 element.

<!DOCTYPE html>
<html>
<head>
<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<script>
$(document).ready(function(){
    $("button").click(function(){
        $("h1").hide();
    });
});
<script>
</head>

<body>
<h1>This is heading1.</h1>

</body>
</html>

This is heading1.

Example 2.2

You can hide more than one elements at one go by adding another hide method to the first method, separated by a ;.

<!DOCTYPE html>
<html>
<head>
<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<script>
$(document).ready(function(){
    $("button").click(function(){
        $("p").hide();$("h2").hide();
    });
});
<script>
</head>
<body>
<h2>This is the title.</h2>
<p>This is the paragraph.</p>
<button>Click me to hide title and paragraph</button>

</body>
</html>

This is the title.

This is the paragraph.





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