Using third-party JavaScript file in Node.js

Question

I have a JavaScript file which is not written for Node.js. It is actually written by me, but this question may be more understandable if you think of it as a third-party library.

Normally, a Node.js module only exposes the module.exports object to external code. This requires the file to be written with Node.js in mind.

However, the file isn't written for Node.js, yet I want to include it into a Node.js module. I can't edit this file, since it will be used later, independently of Node.js.

I imagine I could pull it off by reading the file and calling eval on the contents, but is there a better way?

TL;DR

How can I include a .js file into a Node.js module, without rewriting it to use Node.js-specific code like exports?

P.S. The reason I want to use it in Node.js is for a few tests before it's deployed elsewhere.

Esailija · Accepted Answer · 2012-07-31 22:54:34Z

2

It depends on how the code is written on that file. If the file contains a class or a single object then you can do this:

(function(global) {

    function MyClass() {


    }

    MyClass.prototype = {
            ...
    };

    if( typeof module !== "undefined" && module.exports ) {
        module.exports = MyClass;
    }
    else if ( global ) {
        global.MyClass = MyClass;
    }

})(this);

You can modify the global assignment to be a deeper namespace instead if required.

answered Jul 31, 2012 at 22:54

Esailija

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7 Comments

Esailija Over a year ago

This is the standard way I see in github projects for files that should work in browser as well as node.js.

Kendall Frey Over a year ago

What about for files that should work in other interpreters, like WScript?

Esailija Over a year ago

@KendallFrey then it will attach it to the global object in that environment. Unless it supports module.exports, of course.

Kendall Frey Over a year ago

global is undefined in WScript. I would like this to be available in WScript, so how can I provide compatibility?

Esailija Over a year ago

@KendallFrey global is locally scoped custom variable I created in that function (it might as well be asdasd since it's local), it's passed in the last line this which will evaluate to the global object. After that function has executed, you can access it with this.MyClass when in global context. You can also use any other global object reference that is available in that environment (window, self, etc in browsers), but this keyword is specified to resolve to the global object when in global scope.

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