How to write an ES6 class\module that can be used by NodeJS & Aurelia

Question

I'm trying to share some simple metadata classes between my nodeJS backend and an Aurelia front end. I can require and use the following from my node (v4.3) process:

"use strict";

class PersonMetadata {

    constructor() {
        this.relation = ["Spouse/partner", "Child", "Parent", "Other"];
    }
}

module.exports.PersonMetadata = PersonMetadata;

but it fails to load in the browser after being processed by the typical Aurelia front end build with:

Error: Cannot read property 'exports' of undefined

How can I structure a module with a class that can be shared between node & Aurelia?

Answer 1

Thought I'd reply with how I got this working. Since my server side node code doesn't currently get processed by gulp I created a shared ES6 class that is directly compatible with node v4.X:

"use strict";

class SharedMetadata {

    constructor() {
        this.myOptions = ["Democrat", "Republican", "Other"];
   }
}

exports.SharedMetadata = SharedMetadata;

This class can be use from node like this:

var SharedMetadata = require('../shared/SharedMetadata').SharedMetadata;

var sharedMetadata = new SharedMetadata();

For the front end this file is processed by the normal Aurelia build\transpile step, but the file will have an error with the exports statement.

So I added another gulp build step that runs only on the "shared" files after the transpile step that fixes up the errors and does a "proper" export:

gulp.task('transform-shared', function() {
    return gulp.src(paths.outputShared + '**/*.js')
        .pipe(replace(/exports\.(.*) = (.*);/g, "_export('$1', $2);"))
        .pipe(gulp.dest(paths.outputShared));
});

This replaces the exports statement with:

_export('SharedMetadata ', SharedMetadata );

Then the class can be used like any "normal" Aurelia front end class.

Answer 2

Your best bet in this situation is to use ES6 as the base and then use the compiler (babel or whichever you are using) to get the module in the format that you expect in both the browser and the node.js server.

The common.js format is most commonly used in node.js and all of the formats are good for your Aurelia apps. Your best bet may be to compile both out (like this task does) to both commonjs and amd.

Then you can target amd in your browser and commonjs on the server side.