Detailed explanation of jQuery plug-in packaging steps-JS Tutorial-php.cn

This time I will bring you a detailed explanation of the jQuery plug-in encapsulation steps. What are theprecautions for jQuery plug-in encapsulation? The following is a practical case, let’s take a look.

Extending jQuery plug-ins and methods is very powerful and can save a lot of development time. This article will outline the basics, best practices, and common pitfalls of jQuery plugin development.

1. Getting Started

Writing a jQuery plug-in starts by adding new functional attributes to jQuery.fn. The object attributes added here are The name is the name of your plug-in:

. The code is as follows:

jQuery.fn.myPlugin = function(){ //你自己的插件代码 };

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Where are the symbols that users like very much? It still exists, however, in order to avoid conflicts with other

JavaScriptlibraries, we'd better pass jQuery to a self-executing closed program, where jQuery is mapped as a symbol, so as to avoid the $ sign being used by other Library overwrite.

. The code is as follows:

(function ($) { $.fn.myPlugin = function () { //你自己的插件代码 }; })(jQuery);

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In this closed program, we can use the $ symbol without restriction to represent jQuery functions.

2. Environment

Now, we can start writing the actual plug-in code. However, before that, we must have an idea of the environment in which the plug-in is located. In the scope of the plug-in, the this keyword represents the jQuery object that the plug-in will execute. A common misunderstanding is easy to occur here, because in other jQuery functions that contain callbacks, the this keyword represents the native DOM element. This often causes developers to mistakenly wrap the this keyword in jQuery unnecessarily, as shown below.

. The code is as follows:

(function ($) { $.fn.myPlugin = function () { //此处没有必要将this包在$号中如$(this)，因为this已经是一个jQuery对象。 //$(this)等同于 $($('#element')); this.fadeIn('normal', function () { //此处callback函数中this关键字代表一个DOM元素 }); }; })(jQuery); $('#element').myPlugin();

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3. Basic knowledge

Now, we understand the basic knowledge of jQuery plug-in, Let's write a plugin that does something.

. The code is as follows:

(function ($) { $.fn.maxHeight = function () { var max = 0; this.each(function () { max = Math.max(max, $(this).height()); }); return max; }; })(jQuery); var tallest = $('p').maxHeight(); //返回高度最大的p元素的高度

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This is a simple plug-in that uses .height() to return the height of the p element with the largest height on the page.

4. Maintain Chainability

Many times, the intention of a plug-in is simply to modify the collected elements in some way and pass them on to the next method in the chain. This is the beauty of jQuery's design and one of the reasons jQuery is so popular. Therefore, to maintain a plugin's chainability, you must ensure that your plugin returns the this keyword.

. The code is as follows:

(function ($) { $.fn.lockDimensions = function (type) { return this.each(function () { var $this = $(this); if (!type || type == 'width') { $this.width($this.width()); } if (!type || type == 'height') { $this.height($this.height()); } }); }; })(jQuery); $('p').lockDimensions('width').CSS('color', 'red');

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Since the plugin returns this keyword, it maintains chainability, so that elements collected by jQuery can continue to be controlled by jQuery methods such as .css. Therefore, if your plugin does not return an intrinsic value, you should always return the this keyword within its scope. Additionally, you might deduce that parameters passed to a plugin will be passed within the plugin's scope. Therefore, in the previous example, the string 'width' becomes a type parameter of the plugin.

5. Default values and options

For more complex plug-ins that provide many customizable options, it is best to have a local Default settings that can be extended when the plugin is called (by using $.extend). So instead of calling a plugin with a bunch of parameters, you can call it with an object parameter containing the settings you want to override.

. The code is as follows:

(function ($) { $.fn.tooltip = function (options) { //创建一些默认值，拓展任何被提供的选项 var settings = $.extend({ 'location': 'top', 'background-color': 'blue' }, options); return this.each(function () { // Tooltip插件代码 }); }; })(jQuery); $('p').tooltip({ 'location': 'left' });

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In this example, when calling the tooltip plug-in, the location option in the default settings is overwritten, and the background-color option remains at its default value, so the setting that is finally called The set value is:

. The code is as follows:

{ 'location': 'left', 'background-color': 'blue' }

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This is a very flexible way to provide a highly configurable plug-in without the need for developers to define all available options.

6.Namespace

Properly naming your plug-in is a very important part of plug-in development. With the right namespace, you can guarantee that your plugin will have a very low chance of being overwritten by other plugins or other code on the same page. Namespaces also make your life as a plugin developer easier because it helps you better keep track of your methods, events, and data.

7. Plug-in method

在任何情况下，一个单独的插件不应该在jQuery.fnjQuery.fn对象里有多个命名空间。

. 代码如下:

(function ($) { $.fn.tooltip = function (options) { // this }; $.fn.tooltipShow = function () { // is }; $.fn.tooltipHide = function () { // bad }; $.fn.tooltipUpdate = function (content) { // !!! }; })(jQuery);

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这是不被鼓励的，因为它.fn使.fn命名空间混乱。为了解决这个问题，你应该收集对象文本中的所有插件的方法，通过传递该方法的字符串名称给插件以调用它们。

. 代码如下:

(function ($) { var methods = { init: function (options) { // this }, show: function () { // is }, hide: function () { // good }, update: function (content) { // !!! } }; $.fn.tooltip = function (method) { // 方法调用 if (methods[method]) { return methods[method].apply(this, Array.prototype.slice.call(arguments, 1)); } else if (typeof method === 'object' || !method) { return methods.init.apply(this, arguments); } else { $.error('Method' + method + 'does not exist on jQuery.tooltip'); } }; })(jQuery); //调用init方法 $('p').tooltip(); //调用init方法 $('p').tooltip({ foo: 'bar' }); // 调用hide方法 $(‘p').tooltip(‘hide'); //调用Update方法 $(‘p').tooltip(‘update', ‘This is the new tooltip content!');

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这种类型的插件架构允许您封装所有的方法在父包中，通过传递该方法的字符串名称和额外的此方法需要的参数来调用它们。这种方法的封装和架构类型是jQuery插件社区的标准，它被无数的插件在使用，包括jQueryUI中的插件和widgets。

八、事件

一个鲜为人知bind方法的功能即允许绑定事件命名空间。如果你的插件绑定一个事件，一个很好的做法是赋予此事件命名空间。通过这种方式，当你在解除绑定的时候不会干扰其他可能已经绑定的同一类型事件。你可以通过追加命名空间到你需要绑定的的事件通过 ‘.'。

. 代码如下:

(function ($) { var methods = { init: function (options) { return this.each(function () { $(window).bind('resize.tooltip', methods.reposition); }); }, destroy: function () { return this.each(function () { $(window).unbind('.tooltip'); }) }, reposition: function () { //... }, show: function () { //... }, hide: function () { //... }, update: function (content) { //... } }; $.fn.tooltip = function (method) { if (methods[method]) { return methods[method].apply(this, Array.prototype.slice.call(arguments, 1)); } else if (typeof method === 'object' || !method) { return methods.init.apply(this, arguments); } else { $.error('Method ' + method + ' does not exist on jQuery.tooltip'); } }; })(jQuery); $('#fun').tooltip(); //一段时间之后… … $(‘#fun').tooltip(‘destroy');

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在这个例子中，当tooltip通过init方法初始化时，它将reposition方法绑定到resize事件并给reposition非那方法赋予命名空间通过追加.tooltip。稍后，当开发人员需要销毁tooltip的时候，我们可以同时解除其中reposition方法和resize事件的绑定，通过传递reposition的命名空间给插件。这使我们能够安全地解除事件的绑定并不会影响到此插件之外的绑定。

九、数据

通常在插件开发的时候，你可能需要记录或者检查你的插件是否已经被初始化给了一个元素。使用jQuery的data方法是一个很好的基于元素的记录变量的途径。尽管如此，相对于记录大量的不同名字的分离的data, 使用一个单独的对象保存所有变量，并通过一个单独的命名空间读取这个对象不失为一个更好的方法。

. 代码如下:

(function ($) { var methods = { init: function (options) { return this.each(function () { var $this = $(this), data = $this.data('tooltip'), tooltip = $('', { text: $this.attr('title') }); // If the plugin hasn't been initialized yet if (!data) { /* Do more setup stuff here */ $(this).data('tooltip', { target: $this, tooltip: tooltip }); } }); }, destroy: function () { return this.each(function () { var $this = $(this), data = $this.data('tooltip'); // Namespacing FTW $(window).unbind('.tooltip'); data.tooltip.remove(); $this.removeData('tooltip'); }) }, reposition: function () { // ... }, show: function () { // ... }, hide: function () { // ... }, update: function (content) { // ... } }; $.fn.tooltip = function (method) { if (methods[method]) { return methods[method].apply(this, Array.prototype.slice.call(arguments, 1)); } else if (typeof method === 'object' || !method) { return methods.init.apply(this, arguments); } else { $.error('Method ' + method + ' does not exist on jQuery.tooltip'); } }; })(jQuery);

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将数据通过命名空间封装在一个对象中，可以更容易的从一个集中的位置读取所有插件的属性。

十、总结和最佳做法

编写jQuery插件允许你做出库，将最有用的功能集成到可重用的代码，可以节省开发者的时间，使开发更高效。开发jQuery插件时，要牢记：

1.始终包裹在一个封闭的插件：

. 代码如下:

(function($) { /* plugin goes here */ })(jQuery);

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2.不要冗余包裹this关键字在插件的功能范围内

3.除非插件返回特定值，否则总是返回this关键字来维持chainability 。

4.传递一个可拓展的默认对象参数而不是大量的参数给插件。

5.不要在一个插件中多次命名不同方法。

3.始终命名空间的方法，事件和数据。

最后加一个自己写的放大镜的插件`

(function($){$.fn.Fdj=function(){ $('#smallImg').on('mouseover', function() { $('#slider').show(); }) $('#smallImg').on('mouseout', function() { $('#slider').hide(); }) $('#smallImg').on('mousemove', function(e) { var x = e.clientX - $('#slider').width() / 2; var y = e.clientY - $('#slider').height() / 2; if(x <= 0) { x = 0 } if(x > $('#smallImg').width() - $('#slider').width()) { x = $('#smallImg').width() - $('#slider').width(); } if(y <= 0) { y = 0 } if(y > $('#smallImg').height() - $('#slider').height()) { y = $('#smallImg').height() - $('#slider').height(); } $('#slider').css({ 'left': x, 'top': y }) var X=x/$('#smallImg').width()*800 var Y=y/$('#smallImg').height()*800 $('#img').css({ left:-X, top:-Y }) }) } })(jQuery)

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