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I created two files, app.js and helpers.js and when I tried to call a function from app.js, I got an error, function is not defined.

The two files are located in the same folder. I think there is a problem the module.exports keyword,

can anyone help me here? Here is the code of the two separate files:

//app.js

const helpers= require('./helpers');


const total= sum(10,20);
console.log("total:",total);

//helpers.js

const sum = (a,b)=>{
	return a+b;
}

module.exports={
	sum
};

And the error i am getting is:

const total= sum(10,20);
             ^

ReferenceError: sum is not defined
    at Object.<anonymous> (E:\testing\app.js:5:14)
    at Module._compile (internal/modules/cjs/loader.js:1147:30)
    at Object.Module._extensions..js (internal/modules/cjs/loader.js:1167:10)
    at Module.load (internal/modules/cjs/loader.js:996:32)
    at Function.Module._load (internal/modules/cjs/loader.js:896:14)
    at Function.executeUserEntryPoint [as runMain] (internal/modules/run_main.js:71:12)
    at internal/main/run_main_module.js:17:47
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4
  • You are calling sum before it's created. If you want to keep the sum creation at the same place, you need to make it a function declaration, otherwise you can just move it up. Commented Apr 14, 2020 at 18:13
  • 1
    it will be helpers.sum(10,20); not only sum Commented Apr 14, 2020 at 18:14
  • ...and that's why we ask for a minimal reproducible example. I got mislead by the code since it was not representative. Commented Apr 14, 2020 at 18:16
  • I believe you have to refer to the sum method through the object assigned by the require('./helpers') statement ie const total = helpers.sum(10,20); Commented Apr 14, 2020 at 18:18

4 Answers 4

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1

Try this way:

   //app.js

const helpers= require('./helpers');


const total= helpers.sum(10,20);
console.log("total:",total);

//helpers.js

const sum = (a,b)=> {
    return a+b;
}

module.exports = sum;
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Comments

1

The problem is that you are exporting your function sum in helpers.js within an object:

// helpers.js

// ...

module.exports = {
    sum
};

If you want to access it from app.js you can either use helpers.sum(...) to access it:

// app.js

const helpers = require('./helpers');


const total = helpers.sum(10, 20);
console.log("total:", total);

... or you can use object deconstruction in the require line:

// app.js

const { sum } = require('./helpers');

// ...

Update

Sure, the answer you posted does work, but from the name helpers.js I assume that you might want to put multiple helper functions into that file. Then, you must use an object export - as mentioned above - in order to export all helper functions.

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Comments

0

You can try to edit the way to export the sum function to:

module.exports = sum;

That's because when you define:

module.exports = {...}

it means you're exporting an object, not a function.

Usage:

const sum= require('./helpers');

const total= sum(10,20);
console.log("total:",total);
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Comments

0

Finally, I found a my answer.

I just needed to replace the helpers keyword with sum keyword in the first line of app.js and I also removed the curly braces around sum in helpers.js as per other's advice.

The correct code is below

//app.js

const sum= require('./helpers');
const total= sum(10,20);

console.log("total:",total);

and

//helpers.js

const sum = (a,b)=>{
return a+b;
}
module.exports=sum;
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