How do I call up another JavaScript file from one main file?

Question

I am creating a bot for Discord using the discord.js library. I'm trying to create a file so that when I execute it, it loads up each module without me having to run node file.js multiple times over. The file, which we shall call startup.js, is located in the modules folder. Let's say I want to load File1.js, File2.js, and File3.js which is in Bot/modules/diagnostics, while startup.js is in Bot/modules. I want the files to be loaded asynchronously, and the order is not important.

All help is appreciated.

"... is located in the modules folder but is not in any specific folder" doesn't make much sense. Have you tried [`require()`](https://nodejs.org/api/modules.html#modules_require)? — TypeIA, Jan 25 '18 at 19:31
By not in any specific folder I mean that it's not in, say, diagnostics. It's just in the modules folder. Also yes, I have tried require(). — Alcifer Bijec, Jan 25 '18 at 19:36
I can call in `config.json`, however, I haven't tried it with a JavaScript file. My bad. I'll try that right now. — Alcifer Bijec, Jan 25 '18 at 19:40
Possible duplicate of [How to Use one module feature within another module in nodejs require()](https://stackoverflow.com/questions/13039825/how-to-use-one-module-feature-within-another-module-in-nodejs-require) — Jordan Kasper, Jan 25 '18 at 20:41

MaxxiBoi · Accepted Answer · 2018-02-03T18:06:25.313

You can import File1, File2, and File3 as modules. First method:

    //File1.js:
    module.exports = {
        nameOfYourFunction: () => {
            //Your code here
        },
        otherFunction: (args) => {
            //Your code here
        }
    };
    //Do the same for File2, File3, and other files.

    //startup.js:
    const file1 = require("./diagnostics/File1.js"), file2 = require("./diagnostics/File2.js"), file3 = require("./diagnostics/File3.js");
    // Then use this to run your code from File1.js:
    file1.nameOfYourFunction();
    file1.otherFunction(args);
    //Do the same thing to run your code from other files

Second Method:

    /* If you only have one function that you want to run,
    you can set the module's entire exports to a function. This method will
    not allow you to create multiple functions.*/

    //File1.js:
    module.exports = (args) => {
        //Your code here
    };
    //Do the same thing or the First method for other files.

    //startup.js:
    const file1 = require("./diagnostics/File1.js"), file2 = require("./diagnostics/File2.js"), file3 = require("./diagnostics/File3.js");
    //To run your code:
    file1(args);

Edit: Be careful when you're using these methods because they are in a different scope than the main code in startup.js.

FireController1847 · Answer 2 · 2018-01-27T06:20:54.553

To give a more detailed answer, there are a few ways of being able to do this. The first way to do this is to use module.exports with an object. This will allow you to import the module using require (or, using a compiler like babel or webpack, import), and you can call any function within the object. This is using the method of @MaxxiBoi's response.

// File 1
module.exports = {
   "myFunction1": (arg1, arg2) => {
       console.log("Function 1 with 2 args: "+ arg1 + " " + arg2);
   },
   "myFunction2": () => {
       console.log("Function 2");
   }
}

// File 2
const myModule = require("./file1.js");
myModule.myFunction1(null, "Hi"); // Logs "Function 1 with 2 args: null Hi"
myModule.myFunction2(); // Logs "Function 2"

While this can be useful in situations where you want to output more than one function, if you only want one function per module, I wouldn't do this.

The second method would be using module.exports with a variable or function, instead of an object. This can keep down clutter and make it easier to understand.

// File 1
module.exports = myFunction1(arg1, arg2) {
    console.log("Function 1 with 2 args: " + arg1 + " " + arg2);
}

// File 2
const myFunction = require("./file1.js");
myFunction(null, "Hi"); // Logs "Function 1 with 2 args: null Hi"

Finally, there's another method of creating a constructor using either ES5 or ES6 (for this example I'm using ES6), which will allow you to be able to pass more variables into it that you can then reference within said class. In this example, I'm using a Discord.js client and getting the client's name from the constructor. Assume the client's name is "George".

// File 1
module.exports = class MyClass {
    constructor(client) {
        this.client = client;
    }
    myFunction1(myVar2) {
        console.log("Function 1 with 2 args: " + this.client.user.username + " " + myVar2);
    }
    myFunction2() {
        console.log("Function 2");
    }
}

// File 2
const MyClass = require("./MyClass.js");
const myClassInstance = new MyClass(client);
myClassInstance.myFunction1("Hi"); // Logs "Function1 with 2 args: George Hi"
myClassInstance.myFunction2(); // Logs "Function 2"

In the end, it's all up to what you prefer and how you'd like to do it. Each method has their ups and downs. If you want to learn more about how I made all of these and how modules work in general, check out the Node.js docs explanation. To learn more about classes (the one used in the third module), check out the MDN documentation. Hope I was able to help and give you options. You may also want to take a look at this StackOverflow question, as it will solve your question about referencing a file in a different directory. Happy coding!

How do I call up another JavaScript file from one main file?

2 Answers2