cycle-import-check

circular dependency check tool for javascript modules

ES6 circular import check tool, support js, ts, jsx, tsx and mjs files, and will ignore all node_modules files.

Support import, export keywords and require(), import() function now

Why do we need this tool ?

In javascript ES6 standard, people use import & export keyword in modules, but if js files circular import each other, some exported objects will be undefined in runtime.

The best practice is one-way dependency, and I wrote this tool to ensure no circular-dependency in projects.

Circular dependency sample project

Let's look at a circular dependency example:

file1.js

// and console will be first triggered in file2
import { value2 } from "./file2"; 
// file2 is fully imported
export const value1 = "value1"
// value2 is 'value2'
console.log("value2 in file1: " + value2) 
setTimeout(() => {
  // value2 is 'value2'
  console.log("delay 200ms, value2 in file1: " + value2)
}, 200)

// file1 is fully executed now

file2.js

import { value1 } from "./file1"; 
// file1 is not fully executed, just ref with cache
export const value2 = "value2"  
// value1 is undefined
console.log("value1 in file2: " + value1) 
setTimeout(() => {
  // file1 is executed now
  console.log("delay 200ms, value1 in file2: " + value1) // value1 is 'value1'
}, 200)

> babel-node --presets es2015 file1.js

value1 in file2: undefined
value2 in file1: value2
delay 200ms, value1 in file2: value1
delay 200ms, value2 in file1: value2

If we only have two js files, it's easy to determine wether scripts have circular dependencies.

However, if we have a large project with thousands of files, it's hard to do that.

So, this tool appeared, using old (but efficient) graph algorithms to check for circular dependency.

How to resolve circular dependency ?

Just extract shared variables/functions into an independent file:

from

graph TD
    file1.js -->|value1| file2.js
    file1.js -->|value2| file2.js

to

graph TD
    file1.js -->|value1| value.js
    file2.js -->|value2| value.js

Usage

npx cycle-import-check [a directory path]

detected

> iscan tests/testproject4

Circular dependency existed in tests/testproject4

cycle 1, size (2):

  tests/testproject4/file2.js
  tests/testproject4/file1.js

normal

> iscan tests/testproject2

Congratulation! Not found circular dependency in tests/testproject2

CHANGELOG

LICENSE (MIT)