[javascript] What is the use of the init() usage in JavaScript?

NB. Constructor function names should start with a capital letter to distinguish them from ordinary functions, e.g. MyClass instead of myClass.

Either you can call init from your constructor function:

var myObj = new MyClass(2, true);

function MyClass(v1, v2) 
{
    // ...

    // pub methods
    this.init = function() {
        // do some stuff        
    };

    // ...

    this.init(); // <------------ added this
}

Or more simply you could just copy the body of the init function to the end of the constructor function. No need to actually have an init function at all if it's only called once.