Running Nodejs Function from Dynamic External File

Question

I want to know if there is a way to run a Node function from an external file which is subject to change.

Main.js

function read_external(){
    var external = require('./external.js');
    var result = external.result();
    console.log(result);
}

setInterval(function(){
    read_external();
},3000);

External.js ( Initial )

exports.result = function(){
    return "James"; // Case 1
}

I now run the code by typing node main.js

After the code starts running, I changed the External.js to

exports.result = function(){
    return "Jack"; // Case 2
}

However inspite of the change, it keeps printing James and not Jack. Is there a way to write the code such a way that the new function gets executed when the code is changed ?

I need this as I am building a service where people can provide their own scripts as JS files and it gets executed when they call a certain function in the service depending on who is calling it.

delete require.cache[require.resolve('./external.js')] might be your solution? Just tested and added my comment as an answer. — Ahmet Can Güven
– Ahmet Can Güven, Commented Jul 27, 2017 at 14:34

Ahmet Can Güven · Accepted Answer · 2017-07-27 14:42:18Z

1

You can remove the module from cache before each call.

var module = require.resolve('./external.js');

function read_external(){
    var external = require(module);
    var result = external.result();
    console.log(result);
}

setInterval(function(){
    delete require.cache[module]; //clear cache
    read_external();
},3000);

edited Jul 27, 2017 at 14:42

answered Jul 27, 2017 at 14:38

Ahmet Can Güven

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1 Comment

Ahmet Can Güven Over a year ago

@dontknow You'r welcome :) Just made a little refactoring, please use the latest version.

LoveAndCoding · Accepted Answer · 2017-07-27 14:37:33Z

1

Node.js will cache calls to the same file so it doesn't have to fetch it again. To get the file as if it were new you'll need to clear the cache in require.cache. The key for the file should be the resolved name which you can look up with require.resolve()

answered Jul 27, 2017 at 14:37

LoveAndCoding

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