Pattern for using `main` and `exports` in Node.js

README.md

Pattern for using main and exports in Node.js

Demo

~/src/node-playground(master#%)[0]
$ cat example-main_and_exports.js
#!/usr/bin/env node

const lib = require('./lib.js')

const doA = () => { lib.A() }
const doB = () => { lib.B() }
const doC = () => { lib.C() }

const main = () => {
  doA()
  doB()
  doC()
}

if (require.main === module) {
  main()
} else {
  exports.doA = doA
  exports.doB = doB
  exports.doC = doC
}

bronoric@bruno-mbp:~/src/node-playground(master#%)
$ cat lib.js
#!/usr/bin/false

exports.A = () => { console.log(`Did A.`) }
exports.B = () => { console.log(`Did B.`) }
exports.C = () => { console.log(`Did C.`) }

~/src/node-playground(master#%)[0]
$ ./example-main_and_exports.js
Did A.
Did B.
Did C.

~/src/node-playground(master#%)[0]
$ ./lib.js

~/src/node-playground(master#%)[1]
$ node -e "require('./example-main_and_exports.js').doA()"
Did A.

~/src/node-playground(master#%)[0]
$ node -e "require('./example-main_and_exports.js').doB()"
Did B.

~/src/node-playground(master#%)[0]
$ node -e "require('./example-main_and_exports.js').doC()"
Did C.

example-main_and_exports.js

#!/usr/bin/env node

const lib = require('./lib.js')

const doA = () => { lib.A() }
const doB = () => { lib.B() }
const doC = () => { lib.C() }

const main = () => {
  doA()
  doB()
  doC()
}

if (require.main === module) {
  main()
} else {
  exports.doA = doA
  exports.doB = doB
  exports.doC = doC
}

lib.js

#!/usr/bin/false

exports.A = () => { console.log(`Did A.`) }
exports.B = () => { console.log(`Did B.`) }
exports.C = () => { console.log(`Did C.`) }