requireJS 可选依赖 [英] requireJS optional dependency

问题描述

我正在为我开发的 JavaScript 库添加 AMD 支持.

这个库可能会使用 jquery，但如果没有加载 jquery，它仍然可以工作.

在定义模块依赖项时，有一种方法可以将依赖项设置为可选"，这样如果缺少该库，模块仍然可以工作?

解决方案

我最近遇到了完全相同的问题，以下是我修复它的方法.我定义了一个名为 optional 的 RequireJS 插件，它通过将无法加载的模块显式定义为空对象来忽略它们(但我想你也可以将它定义为 null 或其他任何你想要的东西).>

这是代码(使用 RequireJS 2.1.15 测试):

define("可选", [], {负载:功能(模块名称，parentRequire，onload，配置){var onLoadSuccess = 函数(模块实例){//模块加载成功，调用onload回调使//requirejs 可以发挥它的内在魔法.加载(模块实例)；}var onLoadFailure = 函数(错误){//可选模块加载失败.var failedId = err.requireModules &&err.requireModules[0];console.warn("无法加载可选模块:" + failedId);//取消定义模块以清理 requireJS 中的内部内容requirejs.undef(failedId);//现在将模块实例定义为一个简单的空对象//(注意:您可以在此处返回您想要的任何其他值)定义(failedId, [], function(){return {};});//现在 require 模块确保 requireJS 认为//加载完毕.由于我们刚刚定义了它，requirejs//不会尝试下载更多的脚本文件和//将立即调用 onLoadSuccess 处理程序parentRequire([failedId], onLoadSuccess);}parentRequire([moduleName], onLoadSuccess, onLoadFailure);}});

然后您可以选择使用简单的模块

require(['optional!jquery'], function(jquery){...});

知道如果无法加载jquery模块，传递给你的回调函数的参数将是一个空对象.

I'm adding AMD support to a javascript library I develop.

This library may use jquery but it will still work if jquery isn't loaded.

When defining the module dependency there's a way to set a dependency as 'optional' so that if that library is missing the module will still work?

解决方案

I've had exactly the same problem recently, and here's how I fixed it. I defined a RequireJS plugin called optional which ignores modules that fail to load by explicitly defining them as an empty object (but I suppose you could also define it as null or anything else if you wanted).

Here is the code (tested with RequireJS 2.1.15):

define("optional", [], {
    load : function (moduleName, parentRequire, onload, config){

        var onLoadSuccess = function(moduleInstance){
            // Module successfully loaded, call the onload callback so that
            // requirejs can work its internal magic.
            onload(moduleInstance);
        }

        var onLoadFailure = function(err){
            // optional module failed to load.
            var failedId = err.requireModules && err.requireModules[0];
            console.warn("Could not load optional module: " + failedId);

            // Undefine the module to cleanup internal stuff in requireJS
            requirejs.undef(failedId);

            // Now define the module instance as a simple empty object
            // (NOTE: you can return any other value you want here)
            define(failedId, [], function(){return {};});

            // Now require the module make sure that requireJS thinks 
            // that is it loaded. Since we've just defined it, requirejs 
            // will not attempt to download any more script files and
            // will just call the onLoadSuccess handler immediately
            parentRequire([failedId], onLoadSuccess);
        }

        parentRequire([moduleName], onLoadSuccess, onLoadFailure);
    }
});

You can then require a module optionally using simply

require(['optional!jquery'], function(jquery){...});

knowing that if the jquery module could not be loaded, the parameter passed to your callback function will be an empty object.

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