node.js require() cache - possible to invalidate?

Question

From the node.js documentation:

Modules are cached after the first time they are loaded. This means (among other things) that every call to require(\'

Answer 1

There's a Simple Module for that (with tests)

We had this exact issue while testing our code (delete cached modules so they can be re-required in a fresh state) so we reviewed all the suggestions of people on the various StackOverflow Questions & Answers and put together a simple node.js module (with tests):

https://www.npmjs.com/package/decache

As you would expect, works for both published npm packages and locally defined modules. Windows, Mac, Linux, etc.

How? (usage)

Usage is pretty simple:

install

Install the module from npm:

npm install decache --save-dev

Use it in your code:

// require the decache module:
const decache = require('decache');

// require a module that you wrote"
let mymod = require('./mymodule.js');

// use your module the way you need to:
console.log(mymod.count()); // 0   (the initial state for our counter is zero)
console.log(mymod.incrementRunCount()); // 1

// delete the cached module:
decache('./mymodule.js');

//
mymod = require('./mymodule.js'); // fresh start
console.log(mymod.count()); // 0   (back to initial state ... zero)

If you have any questions or need more examples, please create a GitHub issue: https://github.com/dwyl/decache/issues

Answer 2

The documentation says:

Modules are cached in this object when they are required. By deleting a key value from this object, the next require will reload the module. This does not apply to native addons, for which reloading will result in an error.

Answer 3

Following two step procedure is working perfectly for me.

After changing Model file i-e 'mymodule.js' dynamically, you need to Delete precompiled model in mongoose model first then reload it using require-reload

Example:
        // Delete mongoose model
        delete mongoose.connection.models[thisObject.singular('mymodule')]

        // Reload model
        var reload = require('require-reload')(require);
        var entityModel = reload('./mymodule.js');

Answer 4

I am not 100% certain of what you mean by 'invalidate', but you can add the following above the require statements to clear the cache:

Object.keys(require.cache).forEach(function(key) { delete require.cache[key] })

Taken from @Dancrumb's comment here

Answer 5

If it's for unit tests, another good tool to use is proxyquire. Everytime you proxyquire the module, it will invalidate the module cache and cache a new one. It also allows you to modify the modules required by the file that you are testing.

Answer 6

I made a small module to delete module from the cache after loading. This forces reevaluation of the module next time it is required. See https://github.com/bahmutov/require-and-forget

// random.js
module.exports = Math.random()
const forget = require('require-and-forget')
const r1 = forget('./random')
const r2 = forget('./random')
// r1 and r2 will be different
// "random.js" will not be stored in the require.cache

PS: you can also put "self-destruct" into the module itself. See https://github.com/bahmutov/unload-me

PSS: more tricks with Node require in my https://glebbahmutov.com/blog/hacking-node-require/