Initialize a module when it's required

Question

I have a module with some initialization code inside. The init should be performed when the module is loaded. At the moment I'm doing it like this:

 // in the module

 exports.init = function(config) { do it }

 // in main

 var mod = require('myModule');
 mod.init(myConfig)

That works, but I'd like to be more concise:

 var mod = require('myModule').init('myConfig')

What should init return in order to keep mod reference working?

Ben Fortune · Accepted Answer · 2016-05-12T07:00:10.373

47

You can return this, which is a reference to exports in this case.

exports.init = function(init) {
    console.log(init);
    return this;
};

exports.myMethod = function() {
    console.log('Has access to this');
}

var mod = require('./module.js').init('test'); //Prints 'test'

mod.myMethod(); //Will print 'Has access to this.'

Or you could use a constructor:

module.exports = function(config) {
    this.config = config;

    this.myMethod = function() {
        console.log('Has access to this');
    };
    return this;
};

var myModule = require('./module.js')(config);

myModule.myMethod(); //Prints 'Has access to this'

edited May 12 '16 at 07:00

answered Nov 06 '14 at 11:10

Ben Fortune

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the constructor example doesn't work. Consumer side you should use `new` – alfredopacino Aug 06 '17 at 17:19
How does one do this with the `import` format instead? – lowcrawler May 18 '21 at 22:37

Initialize a module when it's required

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