理解和解决requireJS的报错:MODULE NAME HAS NOT BEEN LOADED YET FOR CONTEXT

使用requireJS加载模块的时候，有时候会碰到如下的错误：

Uncaught Error: Module name "module1" has not been loaded yet for context: _. Use require([])

比如下面的代码就会报这个错误：

require([], function() {
    
	var module = require("module1");
	alert(module.name);
});

这个错误在requireJS官网上写的很明白：
This occurs when there is a require(‘name‘) call, but the ‘name‘ module has not been loaded yet.

我们先来看下，requireJS中定义模块和加载模块的标准方式：

// 加载模块的标准方式
require(['foo','jquery'], function (foo,$) {
    //foo is now loaded.
});

// 定义模块的标准方式
define(['module1', 'module2'], function(m1, m2) {

    return {
        method: function() {
            m1.methodA();
            m2.methodB();
        }
    };

});

如果我们需要加载的或者定义的模块比较少，这种标准的写法是很清晰的。

但是如果我们需要加载的模块很多，那么这种一一对应的写法很繁琐。

define(
    ['dep1', 'dep2', 'dep3', 'dep4', 'dep5', 'dep6', 'dep7', 'dep8'],
    function(dep1, dep2, dep3, dep4, dep5, dep6, dep7, dep8){
        ...
    }
);

方式1：If you are using the simplified define wrapper, make sure you have require as the first argument to the definition function

define(
    function (require) {
        var dep1 = require('dep1'),
            dep2 = require('dep2'),
            dep3 = require('dep3'),
            dep4 = require('dep4'),
            dep5 = require('dep5'),
            dep6 = require('dep6'),
            dep7 = require('dep7'),
            dep8 = require('dep8');
    }
});

define(['require', 'dep1', 'dep2', 'dep3', 'dep4', 'dep5'], function (require) {
    var dep1 = require('dep1');
    var dep2 = require('dep2');
});

但是下面的这种写法就不行，会报错HAS NOT BEEN LOADED YET FOR CONTEXT

//THIS WILL FAIL
define(['require'], function (require) {
    var namedModule = require('name');
});

This fails because requirejs needs to be sure to load and execute all dependencies before calling the factory function above. If a dependency array is given to define(), then requirejs assumes that all dependencies are listed in that array, and it will not scan the factory function for other dependencies. So, either do not pass in the dependency array, or if using the dependency array, list all the dependencies in it.

最后官网上特别强调：require(‘name‘)这种写法，只应该出现在define()或者require()的回调函数中。

Be sure that require(‘name‘) only occurs inside a define() definition function or a require() callback function, never in the global space by its own.

可以看到使用define()定义模块的时候，如果依赖的模块比较少，那么可以使用标准方式；如果依赖的模块很多，那么可以使用方式1或者方式2来解决。很显然，使用require()加载模块的时候，也存在和define()一样的问题。经过我的试验：使用方式2也是可以的。

方式3：使用require加载多个模块的时候

//异步加载module1模块,加载完成后调用回调函数
require(["module3","module1","module2"], function() {
    
	var m1 = require("module1");
	alert(m1.name);
});