Learn how to use JQuery

1. Introduction of jquery

1.1 What is jquery

JQuery is a JavaScript function library.

To put it bluntly, jQuery encapsulates JS and is equivalent to a JS utility class.

JQuery has everything that js has, but it also has a lot of plugins that simplify the code we write.

If JS is the subancient beast of digimon, jQuery is the fighting Tyrannosaur that has evolved and gotten stronger.

1.2 Why jquery

It is compatible with all browsers on the market
Free and open source, small capacity
There are many useful plug-ins
Simplify code. No need to write a bunch of stinky long code inside script tags.

For example, get element node:

Javascript code:var div = document.getElementById("div"); JQuery code:var div = $("div");
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2. Use

Official website download address:

https://jquery.com/download/
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Click on it and you’ll see a lot of messy code. This is the source code for JQuery, copy and paste it as jquery.js.

Then introduce it into your project.

Introduce syntactic formats:

<script type="text/javascript" SRC ="jquery.js file path ">Copy the code

Such as:

<! DOCTYPEhtml>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>A Rebus</title>
    <script src="jquery.js"></script>
</head>
<body>
   
</body>
</html>
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We can also use the online import of jquery.js:

<script src="https://code.jquery.com/jquery-3.1.1.min.js"></script>
<script src="https://cdn.staticfile.org/jquery/1.10.2/jquery.min.js"> .... There are many onlineCopy the code

3. The selector

JQuery’s selectors can manipulate all elements in HTML, which is essentially DOM manipulation.

Get JQuery element nodes starting with $.

3.1 Element selectors

Syntax format:

$(" element ")Copy the code

For example, get the div element node

$("div")
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3.2 ID selector

Syntax format:

$("#id")
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Such as:

<body>
    <p id="p1">Take an examination of grind immediately, wish everybody all go ashore!</p>
    <script>
        var p1 = $("#p1");
    </script>
</body>
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3.3 Class selector

Syntax format:

$(".class")
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Such as:

<body>
    <p class="p2">Take an examination of grind immediately, wish everybody all go ashore!</p>
    <script>
        var p2 = $(".p2");
    </script>
</body>
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3.4 Combinatorial selectors

Combinatorial selectors are comma-separated elements that combine ids, classes, tag names, and so on.

Syntax format:

$("id,class, tag name ")Copy the code

For example, select all div elements with id p1 and class P2.

$("#p1,.p2,div")
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3.5 Form pickers

Form element selectors mainly refer to the selectors of text boxes, checkboxes, checkboxes and other elements.

Select all text boxes

$(":text")
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Select all the password boxes

$(":password")
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Select all the checkboxes

$(":radio")
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Select all the check boxes

$(":checkbox")
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4. DOM manipulation

We learned from DOM trees that in order to change the values of attribute nodes and text nodes, we must first find their element nodes.

So once we get the element node we can manipulate the attribute node and the text information underneath the element node.

4.1 Obtaining/Setting Content

Text () – Sets or returns the text content of the selected element

Such as:

<body>
    <p id="p1">Take an examination of grind immediately, wish everybody all go ashore!</p>
    <script>
        var info = $("#p1").text();
        document.write("<h1>"+info+"</h1>");
    </script>
</body>
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HTML () – Sets or returns the content of the selected element (including HTML elements)

Such as:

<body>
    <p id="p1">Class, the final exam is coming.<b>Have a good day! Before! Before!</b></p>
    <script>
        var info = $("#p1").html();
        document.write("<h1 style='color:red'>" + info + "</h1>");
    </script>
</body>
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Val () – Sets or returns the value of the form field

Such as:

<body>
    <input type="text" style="width: 210px;" value='There's nothing about you but your good looks.'>
    <script>
        var info = $("input").val();
        document.write("<h1 style='color:red'>"+info+"</h1>");
    </script>
</body>
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4.2 Obtaining/Setting Properties

The attr() and prop() methods are used to get and set properties.

Syntax format:

Attr (" Attribute name "," attribute value "); JQuery element node. Prop (" Attribute name "," attribute value ");Copy the code

Such as:

<body>
    <p id="p1">I'm a cute, sexy P-factor</p>
    <a href="http://www.baidu.com">I'm a sentimental hyperlink</a><br>
    <script>
        // Get attributes
       var id = $("#p1").attr("id");
       document.write("P tag id attribute value:"+id+"<br>");
       document.write(The original href value of the a tag:+ $("a").attr("href") +"<br>");
       // Modify attributes
       $("a").attr("href"."https://www.bilibili.com/");
       document.write("Href value after the A tag:"+ $("a").attr("href") +"<br>");
    </script>
</body>
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4.3 Adding Elements

You can use JQuery to add new elements to your HTML code.

Append () – Inserts content at the end of the element.

Such as:

<body>
    <p id="p1">Before my bed a pool of night</p>
    <script>
      $("#p1").append("I think it's frost on the ground.")
    </script>
</body>

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Prepend () – Inserts content at the beginning of the element

Such as:

<body>
    <p id="p1">Raised a pool of gull herons.</p></p>
    <script>
      $("#p1").prepend("Make haste, make haste,")
    </script>
</body>
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Before () – Inserts content before the element

Such as:

<body>
    <h1>He who wants to speak sheds tears first.</h1>
    <script>
      $("h1").before("Things are not everything,")
    </script>
</body>
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After () – Inserts content after the element

Such as:

<body>
    <h1>"Plum Blossom · Red lotus fragrance remnant jade mat autumn" clip</h1>
    <script>
        var txt1 = " A lovesickness, 
";
        var txt2 = $("<p></p>").text("Two sorrows.");
        var txt3 = $("<p></p>").text("There is no remedy for this,");
        var txt4 =  frown, ;
        var txt5 = " is on my mind. 
";
        $("h1").after(txt1, txt2, txt3, txt4, txt5);
    </script>
</body>
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4.4 Deleting Elements

With jQuery, you can easily remove existing HTML elements.

Remove () – Removes the selected element (including child elements)

Such as:

<body>
    <h1>The contents of the following divs have been deleted</h1>
    <div>
        <p>I'm a child of div</p>
    </div>
    <script>
        $("div").remove();
    </script>
</body>
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Empty () – Removes child elements from the selected element

Such as:

<body>
    <h1>The second son in div has been removed</h1>
    <div>
        <p id="p1">I'm Div's oldest son</p>
        <p id="p2">I am div's second son</p>
    </div>
    <script>
        $("#p2").empty();
    </script>
</body>

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4.5 Show/Hide Elements

The show() method displays elements

Such as:

<body>
    <h1>The hidden div comes to the surface</h1>
    <div style="display: none;">
        <p id="p1">I'm Div's oldest son</p>
        <p id="p2">I am div's second son</p>
    </div>
    <script>
        $("div").show();
    </script>
</body>
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The hide() method hides elements

Such as:

<body>
    <h1>The div element is hidden</h1>
    <div style="display: none;">
        <p id="p1">I'm Div's oldest son</p>
        <p id="p2">I am div's second son</p>
    </div>
    <script>
        $("div").hide();
    </script>
</body>
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4.6 Operating the Class Class

You can manipulate the value of the classs attribute of an element using JQuery.

AddClass () – Adds one or more classes to the selected element

Such as:

<! DOCTYPEhtml>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <title>A Rebus</title>
    <script src="https://cdn.staticfile.org/jquery/1.10.2/jquery.min.js"></script>
    <style>
        .pp {
            color: palevioletred;
            font-size: 20px;
        }
    </style>
</head>

<body>
    <p>I'm the prettiest guy on the street!</p>
    <script>
        $("p").addClass("pp");
    </script>
</body>

</html>
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RemoveClass () – Removes one or more classes from the selected element

Such as:

<! DOCTYPEhtml>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <title>A Rebus</title>
    <script src="https://cdn.staticfile.org/jquery/1.10.2/jquery.min.js"></script>
    <style>
        .p1 { color: palevioletred; }
        .p2 { font-size: 20px; }
        .p3 { font-weight: bold; }
    </style>
</head>

<body>
    <p class="p1 p2 p3">You, a look at me, a look at the clouds. I think, when you look at me far away, you look at the clouds very close.</p>
    <script>
        $("p").removeClass("p1");
    </script>
</body>

</html>
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Running results:

4.7 Setting CSS Properties

Set a single CSS property

Such as:

<body>
    <p>Facing the sea, with spring blossoms.</p>
    <script>
        $("p").css("color"."red");
    </script>
</body>
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Set multiple CSS properties

To set multiple CSS properties, use curly braces and key-value pairs.

Such as:

<body>
    <p>I left quietly, as quietly as I came.</p>
    <script>
        $("p").css({"color":"red"."font-size":"30px"});
    </script>
</body>
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4.8 Go through the number group

The each method iterates through the array, calling the function once for each element.

Syntax Format 1:

$. Each (array to iterate over, function(index,element) {handler}) index: the index of the array element: the element in the arrayCopy the code

Syntax Format 2:

Each (function(index, element) {handler}) element: an element in an arrayCopy the code

Example 1:

<script>
  var animals =["cat"."pig"."dog"];
  $.each(animals,function (index,element) {
      document.write("Subscript:+index+"Element:"+element+"<br>");
  })
</script>
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Example 2:

<body>
    <span>Newton</span>
    <span>Einstein</span>
    <span>tesla</span>
    <script>
      $("span").each(function(index,element) {
          document.write(index+""+element.text()+ "</br>");
      })
    </script>
</body>
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5. Events

Events are designed for user interaction. Events are triggered when the user does something, such as pressing a keyboard or clicking a button, to execute the code in the specified function.

Note: The name of the listener event in JQuery is the content after removing on from the JS event.

5.1 DOM Events commonly used by JQuery

The event	describe
click	Click element events
mouseenter	Mouse over an element
mouseleave	Mouse away from an element
hover	Hover over an element
keydown	Press the keyboard
submit	Submit the form
change	The value of the text box changed
focus	Get focus
blur	Lose focus

There are two ways to handle events in JQuery: listening events and binding events.

5.2 Listening Events

Syntax format:

$(selector). The name of the event to listen on (the function that handles the event);Copy the code

Example 1: Listen for click events

<body>
    <p>You click on me, I'll make a box for you</p>
    <script>
        $("p").click(function () {
            alert("You're a real smart cookie.");
        });
    </script>
</body>
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Example 2: Listen for mouse hover events

<body>
    <p>You hover your mouse over me and I have a surprise for you</p>
    <script>
        $("p").hover(function () {
            alert("You are so obedient!!");
        });
    </script>
</body>
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5.3 On Binding Events

The on() method adds an event handler to the selected element.

Syntax format:

. On ("event",data,function) event: One or more events separated by Spaces. Data: Optional. Parameter to be passed in JSON format. Function: optional. Defines the function to execute when an event occurs.Copy the code

Example 1: Bind click events

<body>
    <p>Don't you dare point at me!</p>
    <script>
       $("p").on("click".function () {
           alert("Oh, you are!")})</script>
</body>
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Example 2: Bind mouse hover events

<body>
    <p>Hit Output name</p>
    <h1></h1>
    <script>
       $("p").on("click", {name:"Porgy."},function (event) {$("h1").html(event.data.name);
       })
    </script>
</body>
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6. Execute the method after DOM is loaded

We know that executing code in the script tag when the DOM tree is not fully loaded will result in an error, so we need a DOM loaded entry to execute the method.

$(document).ready(function(){executor});Copy the code

Method 2:

$(function(){executor});Copy the code

Three:

Function ($) {function($)});Copy the code

We usually use method two because of its simple syntax.

7. JQuery example: Caroute diagram

A carousel is a picture that is switched at regular intervals.

So we only need three steps to make a rote map:

The page initializes a photo
Call the interval function setInterval and change the value of the SRC attribute for the image
When the last photo is displayed, it is replaced with the first photo

This time we’ll add a little bit of functionality:

Add button icon, click button to switch pictures
The button is selected along with the image switch

The source code:

<! DOCTYPEhtml>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <title>A Rebus</title>
    <script src="https://cdn.staticfile.org/jquery/1.10.2/jquery.min.js"></script>
    <style>
        #carouseMain {
            width: 400px;
            margin: auto;
        }
        #btnDiv {
            width: 100px;
            border-radius: 40px;
            background-color: rgb(119.117.117);
            margin: auto;
            margin-top: -35px;
            opacity: 0.7;
        }
    </style>
</head>

<body>

    <body>
        <div id="carouseMain">
            <! 1. Initialize a photo -->
            <img src="image/1.jpg" width="400px" height="200px" id="img1" />
        </div>
        <! - button - >
        <div id="btnDiv">
            <input type="radio" name="carouseBtn" id="btn1" value="1" checked>
            <input type="radio" name="carouseBtn" id="btn2" value="2">
            <input type="radio" name="carouseBtn" id="btn3" value="3">
            <input type="radio" name="carouseBtn" id="btn4" value="4">
        </div>

        <script>
            // 2. Call the image modification method every once in a while
            setInterval("changeImg()".2000);

            var i = 0
            function changeImg() {
                i++;
                // 3
                $("#img1").attr("src"."image/" + i + ".jpg");
                // 4. The Settings button is selected
                $("#btn" + i).prop("checked".true);
                // When it is the last image, replace it with the first image
                i = (i== 4)?0 : i;

            }
            // Click button event
            $(':radio').change(function () {
                // The value of the selected button
                var value = this.value;
                $("#img1").attr("src"."image/" + value + ".jpg");
                $("#btn" + value).prop("checked".true);
                i = value;
                i = (i == 4)?0 : i;
            });
        </script>
    </body>
</body>
</html>
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1. Introduction of jquery

1.1 What is jquery

1.2 Why jquery

2. Use

3. The selector

3.1 Element selectors

3.2 ID selector

3.3 Class selector

3.4 Combinatorial selectors

3.5 Form pickers

4. DOM manipulation

4.1 Obtaining/Setting Content

4.2 Obtaining/Setting Properties

4.3 Adding Elements

4.4 Deleting Elements

4.5 Show/Hide Elements

4.6 Operating the Class Class

4.7 Setting CSS Properties

4.8 Go through the number group

5. Events

5.1 DOM Events commonly used by JQuery

5.2 Listening Events

5.3 On Binding Events

6. Execute the method after DOM is loaded

7. JQuery example: Caroute diagram

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