Javascript using function directly and using function that is return from another function

Question

Just out of pure curiosity I have seen codes like below

let GlobalActions = function () {

    let doSomething= function () {
        //Do Something
    };

    return {
        doSomething: function () {
            doSomething()
        }
    };
}();

GlobalActions.doSomething();

At first, I thought it was about scoping, maybe var declared variables from outside is not accessible from each functions inside after it has been initialized; however, that was not true.

Then it came to me thinking what is the advantage of doing the above instead of the below?

let GlobalActions = {

    doSomething: function () {
        //Do Something
    };

};

GlobalActions.doSomething();

This is the so-called "module pattern" that is used for private members, see Private Members in JavaScript. There are many, many questions here already (so this is likely a duplicate of some of them, maybe why module pattern?). — RobG
– RobG, Commented Jan 3, 2018 at 3:14

Bradley Flood · Accepted Answer · 2018-01-03 03:14:52Z

1

Looks to me like The Revealing Module Pattern.

Essentially the returned object provides the "API" interface to the entire class. We can then choose what is exposed as public and what remains private. Eg.

var myRevealingModule = (function () {

        var privateVar = "Ben Cherry",
            publicVar = "Hey there!";

        function privateFunction() {
            console.log( "Name:" + privateVar );
        }

        function publicSetName( strName ) {
            privateVar = strName;
        }

        function publicGetName() {
            privateFunction();
        }

        // Reveal public pointers to
        // private functions and properties

        return {
            setName: publicSetName,
            greeting: publicVar,
            getName: publicGetName
        };

    })();

myRevealingModule.setName( "Paul Kinlan" );

answered Jan 3, 2018 at 3:14

Bradley Flood

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2 Comments

RobG Over a year ago

The "publicVar" isn't public, it's private. It's set by the privileged function publicSetName.

forJ Over a year ago

So it would exactly be same as using class?

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