Packaging JavaScript Functions

Question

I'm working to create a shared package of JavaScript functions. At this time, I'm trying to use them like this:

/app/index.js

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

myPackage.function1();
myPackage.myScope.function2();

The above successfully loads myPackage. However, when I attempt to run function1, I receive an error that says: "TypeError: myPackage.function1 is not a function". My code in the "package" is organized like this:

/myPackage
 index.js
 root
   function1.js
 myScope
   function2.js

The code looks like this:

index.js

require('./root/function1.js');
require('./myScope/function2.js');

function1.js

exports.function1 = function() {
  console.log("Doing stuff in function1");
}

function2.js

exports.function2 = function() {
  console.log("Doing stuff for function2");
}

I could understand function2 not working because, there's nothing putting it in myScope, which I don't know how to do. However, I don't understand why function1 isn't running. What am I doing wrong?

Munim Munna · Accepted Answer · 2019-04-02 14:11:51Z

1

+50

To elaborate bergi's answer, you need to have the following in your index.js file:

// file: index.js
exports.function1 = require('./root/function1.js').function1;
exports.myScope2 = {
    function2: require('./myScope/function2.js').function2,
};

Because require('./root/function1.js') == exports object in function1.js. So if you have multiple functions in your function1.js, you have to go like this:

// file: index.js
exports.function1 = require('./root/function1.js').function1;
exports.function11 = require('./root/function1.js').function11;
exports.function111 = require('./root/function1.js').function111;
...

A shortcut of that can be:

// file: index.js
Object.assign(exports, require('./root/function1.js'));

On the other hand: you can set the exports object to be your function:

// file: function1.js
module.exports = function() {
    console.log("Doing stuff in function1");
}

Then you can have the following in your index.js file:

// file: index.js
exports.function1 = require('./root/function1.js');
exports.myScope2 = {
    function2: require('./myScope/function2.js'),
};

Here require('./root/function1.js') == function1 from function1.js. Hope that explains the issue.

answered Apr 2, 2019 at 14:11

Munim Munna

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6 Comments

user687554 Over a year ago

@MunimMunna What does the /app/index.js file look like then? When I try this, I still get runtime errors.

Munim Munna Over a year ago

index.js looks exactly like the first code-block in the answer, just copy paste. What error do you get?

user687554 Over a year ago

@MunimMunna I see "TypeError: myPackage.function1 is not a function". I added a console.log(myPackage) just before the call to see what was there. I see this: { function1: undefined }

user687554 Over a year ago

@MunimMunna I should mention that if I use require('./root/function1.js') instead of require('./root/function1.js').function1 I see { function1: {} } from the console.log. However, I see the same error.

user687554 Over a year ago

@MunimMunna I got it working. I had to add module.exports = function1; to the bottom of function1.js.

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Bergi · Accepted Answer · 2019-03-31 11:04:52Z

1

Your index.js doesn't export anything. You will have to do

Object.assign(exports, require('./root/function1.js'));
exports.myScope = require('./myScope/function2.js');

Or maybe better have your function1.js and function2.js modules export the function itself (module.exports = function() { … };) instead of creating a property, then use

exports.function1 = require('./root/function1.js');
exports.myScope = {
    function2: require('./myScope/function2.js'),
};

answered Mar 31, 2019 at 11:04

Bergi

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8 Comments

user687554 Over a year ago

If I use exports.function1 = ..., I then have to use myPackage.function1.function1 in my code. I just want to use myPackage.function1.

Bergi Over a year ago

@user687554 You'd do that if you change the export inside the /root/function1.js - a file with that name would be expected to export only that function, not a module object containing that function.

user687554 Over a year ago

So, "function1.js" would be changed to just function function1() { console.log("Doing stuff in function1"); } Is that correct?

Bergi Over a year ago

No, to modules.export = function function1() { …};. The important part is omitting the property from the assignment.

user687554 Over a year ago

I'm sorry, I don't understand what you mean. Which assignment? What should index.js look like?

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