Can somebody explain this javascript fragment?

Question

// JavaScript source code
var foo = (function () {
    var o = { bar: "bar" };

    return {
        bar: function () {
            console.log(o.bar);
        }
    };

})();

foo.bar();

What is going on? Is foo an object? Is it a named function? This looks like a hideous way to provide the class concept of private data members....

Answer 1

They are called IIFE's https://developer.mozilla.org/en-US/docs/Glossary/IIFE

Check this example where IIFE's are used http://javascriptissexy.com/understand-javascript-closures-with-ease/

Usually javascript modules are written in the pattern.

var foo = function () {
    var o = { bar: "bar" };

    return {
        bar: function () {
            console.log(o.bar);
        }
    };

};

foo().bar();

AND

var foo = (function () {
    var o = { bar: "bar" };

    return {
        bar: function () {
            console.log(o.bar);
        }
    };

})();

foo.bar();

are similar.