How to extend jquery plug-in

jQuery is a very popular JavaScript library that is widely used in Web front-end interface development. Many developers write their own jQuery plug-ins to meet their own needs or share them with other developers. The extension of plug-ins is also very important, because it can make plug-ins more flexible and powerful. This article will introduce how to extend jQuery plug-in.

1. The basic structure of jQuery plug-in

Before writing a jQuery plug-in, you need to understand its basic structure. Generally speaking, a simple jQuery plug-in contains at least the following parts:

1. Use anonymous functions to wrap the entire plug-in

(function($) {
/ / your plugin code here
})(jQuery);

This way of writing is to avoid the pollution of global variables.

2. Define the name and default options of the plug-in

$.fn.myPlugin = function(options) {
var settings = $.extend({

option1: 'default value',
option2: 123,
option3: true

}, options );
}

The $.extend method is used here to merge the default options and user-defined options together.

3. Writing the main functions of the plug-in

$.fn.myPlugin = function(options) {
var settings = $.extend({

option1: 'default value',
option2: 123,
option3: true

}, options );

// your plugin code here
// Note: this in the plugin points to the jQuery object, not the DOM element.
}

Here you can write the corresponding function code as needed.

4. Support chain calls

$.fn.myPlugin = function(options) {
var settings = $.extend({

option1: 'default value',
option2: 123,
option3: true

}, options );

// your plugin code here

// Supports chain calls
return this;
}

This will generally be returned Raw jQuery object to support chained calls.

2. Extend the jQuery plug-in

Now let’s take a look at how to extend an existing jQuery plug-in. The following assumes that we want to extend the jQuery.validate plug-in.

1. Use the $.fn.extend() method

$.fn.extend({
myFunction: function() {

console.log('This is my function.');

}
});

This will add a method named myFunction to the jQuery object.

2. Use the $.validator.addMethod() method

$.validator.addMethod('myRule', function(value, element) {
return this. optional(element) || /^[a-zA-Z] $/.test(value);
}, 'Please enter English letters.');

A rule named myRule is defined here Validation rules for verifying whether they are English letters.

3. Modify the default options

$.validator.setDefaults({
highlight: function(element) {

$(element).addClass('highlight');

},
unhighlight: function(element) {

$(element).removeClass('highlight');

}
});

The default highlighting and unhighlighting methods are modified here and changed to add or delete the highlight class .

4. Override a method

$.validator.prototype.showLabel = function(element, message) {
var label = this.errorsFor(element) ;
if (label.length) {

// 修改错误提示信息
label.removeClass(this.settings.validClass).addClass(this.settings.errorClass);
label.html(message || "");

} else {

// 显示错误提示信息
label = $('<' + this.settings.errorElement + '/>', {
  'for': this.idOrName(element),
  generated: true
})
  .addClass(this.settings.errorClass)
  .addClass('highlight')
  .attr('generated', true)
  .html(message || "");

if (this.settings.wrapper) {
  // 将错误提示信息包在指定的容器中
  label = label.hide().show().wrap('<' + this.settings.wrapper + '/>').parent();
}
if (!this.labelContainer.append(label).length)
  this.settings.errorPlacement
  ? this.settings.errorPlacement(label, $(element))
  : label.insertAfter(element);

}
};

The showLabel method is overridden here for modification The default error message style of the plug-in.

Summary

Through the above examples, we can see that the method of extending the jQuery plug-in is very simple, and you only need to make corresponding modifications as needed. Extension plug-ins can not only meet your own needs, but also benefit other developers, so you should consider its extensibility when writing jQuery plug-ins.

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