How JQuery defines CSS

JQuery is a popular JavaScript library that provides a rich API to simplify DOM manipulation and AJAX application development, while providing some built-in functions to manipulate CSS styles. In this article, we will introduce how JQuery defines CSS.

1. JQuery’s CSS methods

In JQuery, you can use CSS methods to set or modify the CSS properties of elements. CSS methods have two forms:

1. CSS(property, value)

You can modify the CSS properties of an element by passing two parameters. The first parameter is the name of the CSS property to be modified, and the second parameter is the value of the property.

For example:

$("p").css("color", "red");

This example will set the color of all p elements to red. You can use any CSS property value such as "border", "background-color", etc.

2. CSS(properties)

Multiple CSS properties of an element can be modified by passing a properties object. This object contains the properties to be changed and their values, as shown below:

$("p").css({
    "color": "red",
    "background-color": "yellow",
    "font-size": "20px"
});

This example sets the color of all p elements to red, the background color to yellow, and the font size to 20 pixels.

Note that we use dashes in the object to represent CSS property names, but dashes are not allowed as object property names in JavaScript, so we need to enclose them in quotes.

2. JQuery’s addClass and removeClass methods

In addition to using CSS methods to define CSS properties, we can also use the addClass and removeClass methods to modify the class name of an element.

1. addClass(class)

The addClass method can add one or more class names to the specified element. For example:

$("p").addClass("highlighted");

This example will add the class names of all p elements to highlighted. You can use spaces to separate multiple class names, such as "highlighted border".

2. removeClass(class)

The removeClass method can remove one or more from the specified element Class name. For example:

$("p").removeClass("highlighted");

This example will delete the highlighted class in all p elements. You can also delete multiple class names at the same time, such as "highlighted border".

3. JQuery's toggleClass method

The toggleClass method can switch class names on the element. If the class name already exists in the element, it will remove the class name from the element; if the class name does not exist in the element, it will add the class name to the element.

For example:

$("p").toggleClass("highlighted");

This example will switch the highlighted class in all p elements. If the class name already exists in the element, then it removes the class name from the element.

4. Summary

JQuery provides a variety of methods to define CSS properties, including CSS methods, addClass methods, removeClass methods and toggleClass methods. These methods make manipulating CSS properties very simple. When using these methods, we need to be careful not to overuse them, as a large number of DOM operations will affect page performance.

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