在浏览器中运行时，可指定路径的备选(fallbacks)，以实现诸如首先指定了从CDN中加载，一旦CDN加载失败则从本地位置中加载这类的机制。
shim: 为那些没有使用define()来声明依赖关系、设置模块的"浏览器全局变量注入"型脚本做依赖和导出配置。
下面有个示例，它需要 RequireJS 2.1.0+，并且假定backbone.js、underscore.js 、jquery.js都装于baseUrl目录下。如果没有，则你可能需要为它们设置paths config：
requirejs.config({
//Remember: only use shim config for non-AMD scripts,scripts that do not already call define().
//The shimconfig will not work correctly if used on AMD scripts,
//in particular, the exports and init config will notbe triggered, and the deps config will be confusingfor those cases.
shim: {
'backbone': {
//These script dependencies should be loaded before loadingbackbone.js|译|在加载backbone.js之前应先加载它的依赖函数underscore.js和jquery.js
deps: ['underscore', 'jquery'],
//Once loaded, use the global 'Backbone' as themodule value.|译|加载完毕后该模块使用的引用名
exports: 'Backbone'
},
'underscore': {
exports: '_'
},
'foo': {
deps: ['bar'],
exports: 'Foo',
init: function (bar) {
//Using a function allows you to call noConflict forlibraries that support it, and do other cleanup.
//However, plugins for those libraries may still want a global.
//"this" for the function will be the global object.
//The dependencies will be passed in as function arguments.
//If this function returns a value,then that value is used as the module export valueinstead of the object found via the 'exports' string.
//Note: jQuery registers as an AMD module via define(),so this will not work for jQuery.
//See notes sectionbelow for an approach for jQuery.
return this.Foo.noConflict();
}
}
}
});
//Then, later in a separate file, call it 'MyModel.js', a module is defined,specifting 'backbone' as a dependency.
//RequireJS will use the shim config to properly load 'backbone' and give a local reference to this module.
//The global Backbone will still exist on the page too.
define(['backbone'], function (Backbone) {
return Backbone.Model.extend({});
});
RequireJS 2.0.*中，shim配置中的"exports"属性可以是一个函数而不是字串。这种情况下它就起到上述示例中的"init"属性的功能。 RequireJS 2.1.0+中加入了"init"承接库加载后的初始工作，以使exports作为字串值被enforceDefine所使用。
那些仅作为jQuery或Backbone的插件存在而不导出任何模块变量的"模块"们，shim配置可简单设置为依赖数组：
requirejs.config({
shim: {
'jquery.colorize': ['jquery'],
'jquery.scroll': ['jquery'],
'backbone.layoutmanager': ['backbone']
}
});
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