Question

作为Javascript中的设计模式的新手，我遇到了模块模式，但我没有得到命名空间的东西。

在the namespacing part of Addy Osmani's online book about JS Design Patterns中，Addy解释了检查变量/名称空间存在的5种方法：

// This doesn't check for existence of "myApplication" in
// the global namespace. Bad practice as we can easily
// clobber an existing variable/namespace with the same name
var myApplication = {};

// The following options *do* check for variable/namespace existence. 
// If already defined, we use that instance, otherwise we assign a new 
// object literal to myApplication.
// 
// Option 1: var myApplication = myApplication || {};
// Option 2  if( !MyApplication ){ MyApplication = {} };
// Option 3: window.myApplication || ( window.myApplication = {} );
// Option 4: var myApplication = $.fn.myApplication = function() {};
// Option 5: var myApplication = myApplication === undefined ? {} : myApplication;

我真正没有得到的是如何解决命名问题。

假设myApplication是在我的代码尝试使用myApplication之前设置的。例如，使用选项1（或实际上所有选项），似乎在myApplication已被使用但仅覆盖myApplication的先前值时没有改变任何内容：

// Higher in some script, where I don't know about it
var myApplication = 'whatever string or object used by the script';

// A bit of code later, where I come with my little Module Pattern
var myApplication = myApplication || {}; // Using Option 1

myApplication = (function($) {
   var myAppVariable = 'blabla';

   var myAppFunction = function() {
       // Doing a few things here
   };

   return myAppFunction;
}) (jQuery);

// Using the module
myApplication.myAppFunction();

对我而言，这是非常令人困惑的，因为我看不出它如何阻止我踩到别人的脚趾。

Answer 1

当您在javascript中加载模块时，您可能（取决于我猜的代码）将不得不覆盖模块命名空间中已有的任何变量。用于保存在加载之前保存模块名称的任何内容的流行模式是noConflict()模式。这种模式背后的想法是在变量中保存命名空间的原始值，如果调用noConflict，则用原始值替换命名空间并返回库。这种模式可以或多或少地优雅地写成：

myModule = "some stuff ya";

(function(namespace, undefined) {
    var _module = "myModule";
    var __originalModule = namespace[_module];//holds the original value in case you wish to restore it

    /****** Code your module here following whichever module pattern you wish to follow ****/
    var module = {
        log: function() {
            if(console.log) {
                console.log(arguments);
            }
        }
    }
    /****** End of your module ****/

    //calling this method will remove your module from the namespace and replace it with whatever
    // originally held your module name.
    //This function returns your module
    module.noConflict = function() {
        namespace[_module] = __originalModule;
        return module;
    }

    namespace[_module] = module; //add your module to the namespace

})(window);

console.log(window.myModule); // => {log: function...}
var myMod = window.myModule.noConflict();
console.log(window.myModule); // => "some stuff ya"

检查全局命名空间中是否存在变量而没有备用名称

1 个答案: