delcache

delcache

Delete module cache safely. This project is inspired by decache.

Installation

# use npm
npm install delcache
# or use yarn
yarn global add delcache

Environment

Node.js 10+

Background

Deleting module cache is the precondition of 'hot reloading'. Typically, we delete the module cache by:

delete require.cache[require.resolve('xxx')]

However, this method can cause memory leakage. It clears the module cache in Module._cache which is referenced by require.cache, but it doesn't eliminate the reference in the array of xxx.parent.children.

delcache provides a way to eliminate both kinds of reference:

delcache('xxx')

In most cases, this is enough to clean up all references, with the following exception:

{
    id: 'parentModule',
    children: [{
        id: 'childModuleA',
        children: [{
            id: 'targetModule'
        }]
    }, {
        id: 'childModuleB',
        children: [{
            id: 'targetModule'
        }]
    }]
}

You will find targetModule still in the children of childModuleA after calling delcache(targetModule) in childModuleB. In this condition, you can pass true as the second argument to delcache: delcache(targetModule, true). delcache will traverse the whole module tree to delete targetModule from children of every module.

When passing rootPath as the third argument, delcache will take it as the starting point. It is a recommended way to save time traversing the module tree.

Usage

Delete cache of target module and clear reference in parent's children:

const delcache = require('delcache')

let five = require('./five')

five.num = 6

delcache('./five')

five = require('./five')

console.log(five.num) // 5

Pass true as the second argument to delete cache of target module from the whole module tree.

const delcache = require('delcache')

let five = require('./five')

five.num = 6

delcache('./five', true)

five = require('./five')

console.log(five.num) // 5

When the second argument is true, you can specify the rootPath from which clear the reference of the target module.

This is a recommended way to make the delete operation faster:

const delcache = require('delcache')

let five = require('./five')

five.num = 6

delcache('./five', true, '../../root')

five = require('./five')

console.log(five.num) // 5

Notice

Don't uese delete require.cache[xxx] with delcache, cause delcache will check if a module is referenced by Module._cache.

//parent.js
require('./a')
require('./b')
//a.js
require('./mod')
delete require.cache[require.resolve('./mod')]
//b.js
const delcache = require('delcahce')
delcache('./mod', true) // delcache can not eliminate the reference of mod in children of a.js