Detailed introduction to jQuery plug-in development

Preface

jQuery plug-in development includes two types:

1. Add static methods to jQuery

2. Prototype for jQuery Add method

Add static method to jQuery

1. Add new global function directly

jQuery.foo = function() {
alert('This is a test. This is only a test.');
}

2. Use jQuery.extend(object)

jQuery.extend({
foo: function() {
alert('This is a test. This is only a test.');
},
bar: function(param) {
alert('This function takes a parameter, which is "' + param +'".');
}
});

For some globally configured plug-ins, you can call them in the plug-in, so you can directly reference the plug-in javascript without calling

to jQuery. Prototype adding method

This is the most commonly used method in plug-in development

The simplest form

(function($){       
    $.fn.pluginName = function() {     
         // code    
    };     
})(jQuery);

Context

The immediate effect of the plug-in function In the domain, the keyword this points to the jQuery object that calls the plug-in, and there is no need to wrap it with $

(function($){
    $.fn.pluginName = function() {      
        // 没有必要再写$(this)，因为"this"就是jQuery对象             
    };          
})(jQuery);

Maintain chained calls

In order to maintain chained calls, the plug-in please return this.

Set default parameters and expose them

(function($){
    $.fn.pluginName = function(options) {    
        var opts = $.extend({}, $.fn.hilight.defaults, options);      
    };  

    $.fn.pluginName.defaults = {    
        foo: 'bar'   
    };                      
})(jQuery);

This way users can either pass parameters or modify the default parameters by modifying $.fn.pluginName.defaults

Expose some public functions

(function($){
    $.fn.pluginName = function(options) {    
        var opts = $.extend({}, $.fn.pluginName.defaults, options);      
    };  

    $.fn.pluginName.defaults = {    
        foo: 'bar'   
    };  

    $.fn.pluginName.foo = function() {    
        return 'bar';    
    };                  
})(jQuery);

so that users can both call public functions and modify them.

A safer way to write closures

;(function($,window,document,undefined){
    $.fn.pluginName = function() {     
         // code    
    };
})(jQuery,window,document);

Adding ";" is to prevent errors caused by the absence of ";" in the previous code of the plug-in. Adding window and document is like this. System variables such as window are in There is a local reference inside the plug-in, which can improve the access speed. At the same time, these variables can also be compressed internally. Undefined is to prevent others from accidentally modifying undefined and causing plug-in bugs.

More

The following is from a netizen’s blog

(function () {   
    var Plugin,
        privateMethod;  //插件的私有方法
     
    /**
     * 这里是一个自运行的单例模式。
     * 
     */
    Plugin = (function () {
 
        /**
         * 插件实例化部分，初始化时调用的代码可以放这里
         */
        function Plugin(element, options) {
            //将插件的默认参数及用户定义的参数合并到一个新的obj里
            this.settings = $.extend({}, $.fn.plugin.defaults, options);
            //将dom jquery对象赋值给插件，方便后续调用
            this.$element = $(element);
             
        }
 
        /**
         * 插件的公共方法，相当于接口函数，用于给外部调用
         */
        Plugin.prototype.doSomething = function () {
            /**
             * 方法内容
             */
        };
         
        return Plugin;
 
    })();
 
    /**
     * 插件的私有方法
     */
    privateMethod = function () {
     
    };
 
    /**
     * 这里是关键
     * 定义一个插件 plugin
     */
    $.fn.plugin = function (options) {
        var instance;
        instance = this.data('plugin');
        /**
         *判断插件是否已经实例化过，如果已经实例化了则直接返回该实例化对象
         */
        if (!instance) {
            return this.each(function () {
                //将实例化后的插件缓存在dom结构里（内存里）
                return $(this).data('plugin', new Plugin(this, options));
            });
        }
        if (options === true) return instance;
        /**
         * 优雅处： 如果插件的参数是一个字符串，则 调用 插件的 字符串方法。
         * 如 $('#id').plugin('doSomething') 则实际调用的是 $('#id).plugin.doSomething();
         * doSomething是刚才定义的接口。
         * 这种方法 在 juqery ui 的插件里 很常见。
         */
        if ($.type(options) === 'string') instance[options]();
        return this;
    };
     
    /**
     * 插件的默认值
     */
    $.fn.plugin.defaults = {
        property1: 'value',
        property2: 'value'
    };
 
    /**
     * 优雅处： 通过data-xxx 的方式 实例化插件。
     * 这样的话 在页面上就不需要显示调用了。
     */
    $(function () {
        return new Plugin($('[data-plugin]'));
    });   
}).call(this);

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