requireJS可选依赖项

Question

我正在为我开发的javascript库添加AMD支持.

这个库可能使用jquery但是如果没有加载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,模块仍然可以工作吗？

Answer 1

我最近遇到了完全相同的问题,这就是我修复它的方法.我定义了一个RequireJS插件optional,它通过显式地将它们定义为空对象来忽略无法加载的模块(但我想你也可以将它定义为null或其他任何你想要的).

这是代码(使用RequireJS 2.1.15测试):

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);
    }
});

然后,您可以选择简单地使用模块

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

知道如果无法加载jquery模块,传递给回调函数的参数将是一个空对象.

Answer 2

您无法将其设置为可选,但您可以捕获错误并使用undef以下命令卸载模块:

require(['jquery'], function ($) {
    //Do something with $ here
}, function (err) {
    //The errback, error callback
    //The error has a list of modules that failed
    var failedId = err.requireModules && err.requireModules[0];
    if (failedId === 'jquery') {
        //undef is function only on the global requirejs object.
        //Use it to clear internal knowledge of jQuery. Any modules
        //that were dependent on jQuery and in the middle of loading
        //will not be loaded yet, they will wait until a valid jQuery
        //does load.
        requirejs.undef(failedId);
        ...
     }
});

完整的例子在这里.