Question

117

ES6 export default with multiple functions referring to each other

rated 0 times [ 120] [ 3] / answers: 1 / hits: 161818 / 9 Years ago, fri, october 16, 2015, 12:00:00

in es6 there you can define a module of functions like this

export default {

    foo() { console.log('foo') }, 

    bar() { console.log('bar') },

    baz() { foo(); bar() }

}

the above seems to be valid code, but if I call baz() it throws an error:

ReferenceError: foo is not defined

How do you call foo from another function? in this case baz

Edit

Here's the code that actually doesn't work. I have simplified the code so it's only the core as needed

const tokenManager =  {

  revokeToken(headers) { 

    ... 

  },

  expireToken(headers) {

    ...

  },

  verifyToken(req, res, next) {

    jwt.verify(... => {

      if (err) {

        expireToken(req.headers)

      }

    })

  }

}



export default tokenManager

and the error is

expireToken(req.headers);

        ^

ReferenceError: expireToken is not defined

Edit 2

I just tried adding tokenManager before expireToken and it finally works

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deonkalvinw

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answered 9 Years ago ammonderekm · Accepted Answer

The export default {...} construction is just a shortcut for something like this:

const funcs = {

    foo() { console.log('foo') }, 

    bar() { console.log('bar') },

    baz() { foo(); bar() }

}



export default funcs

It must become obvious now that there are no foo, bar or baz functions in the module's scope. But there is an object named funcs (though in reality it has no name) that contains these functions as its properties and which will become the module's default export.

So, to fix your code, re-write it without using the shortcut and refer to foo and bar as properties of funcs:

const funcs = {

    foo() { console.log('foo') }, 

    bar() { console.log('bar') },

    baz() { funcs.foo(); funcs.bar() } // here is the fix

}



export default funcs

Another option is to use this keyword to refer to funcs object without having to declare it explicitly, as @pawel has pointed out.

Yet another option (and the one which I generally prefer) is to declare these functions in the module scope. This allows to refer to them directly:

function foo() { console.log('foo') }

function bar() { console.log('bar') }

function baz() { foo(); bar() }



export default {foo, bar, baz}

And if you want the convenience of default export and ability to import items individually, you can also export all functions individually:

// util.js



export function foo() { console.log('foo') }

export function bar() { console.log('bar') }

export function baz() { foo(); bar() }



export default {foo, bar, baz}



// a.js, using default export



import util from './util'

util.foo()



// b.js, using named exports



import {bar} from './util'

bar()

Or, as @loganfsmyth suggested, you can do without default export and just use import * as util from './util' to get all named exports in one object.