问题描述
来自 node.js 文档:
From the node.js documentation:
模块在第一次加载后被缓存.这意味着(除其他外)每次调用 require('foo') 都会返回完全相同的对象,如果它解析为同一个文件.
有没有办法使这个缓存失效?即对于单元测试,我希望每个测试都在一个新对象上工作.
Is there a way to invalidate this cache? i.e. for unit testing, I'd like each test to be working on a fresh object.
推荐答案
您始终可以安全地删除 require.cache 中的条目而不会出现问题,即使存在循环依赖项也是如此.因为当你删除的时候,你只是删除了一个对缓存模块对象的引用,而不是模块对象本身,模块对象不会被GCed,因为在循环依赖的情况下,仍然有一个对象引用这个模块对象.
You can always safely delete an entry in require.cache without a problem, even when there are circular dependencies. Because when you delete, you just delete a reference to the cached module object, not the module object itself, the module object will not be GCed because in case of circular dependencies, there is still a object referencing this module object.
假设你有:
脚本 a.js:
var b=require('./b.js').b;
exports.a='a from a.js';
exports.b=b;
和脚本b.js:
var a=require('./a.js').a;
exports.b='b from b.js';
exports.a=a;
当你这样做时:
var a=require('./a.js')
var b=require('./b.js')
你会得到:
> a
{ a: 'a from a.js', b: 'b from b.js' }
> b
{ b: 'b from b.js', a: undefined }
现在如果你编辑你的 b.js:
now if you edit your b.js:
var a=require('./a.js').a;
exports.b='b from b.js. changed value';
exports.a=a;
然后做:
delete require.cache[require.resolve('./b.js')]
b=require('./b.js')
你会得到:
> a
{ a: 'a from a.js', b: 'b from b.js' }
> b
{ b: 'b from b.js. changed value',
a: 'a from a.js' }
===
以上在直接运行node.js时有效.但是,如果使用具有自己的模块缓存系统的工具,例如 jest,则正确的说法是:
The above is valid if directly running node.js. However, if using tools that have their own module caching system, such as jest, the correct statement would be:
jest.resetModules();
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