Question

I am looking for correct way to add “static” methods (class level methods) into Object and all its children in JavaScript.

I am trying to do:

Object.prototype.myMethod = function() { ... };  
// actually I need only class level method
// but it creates instance method too

I am getting wanted:

function MyClass() {};
var mc = new MyClass();

mc.myMethod();

But I am getting also unwanted:

mc.someProperty = 'val';

for (var k in mc) {
  console.log(k);
}

// => myMethod (this is unwanted)
// => someProperty

How to add only class method into Object and all it’s children without adding of instance method’s?

Answer 1

The code is correct, your loop has to be altered:

for (var k in mc) {
    if (mc.hasOwnProperty(k)) {// Ignores inherit methods/properties
       console.log(k);
    }
}

An alternative solution is by using the Object.defineProperty method to make the element not-enumerable:

Object.defineProperty(mc.prototype, 'myMethod', {
    value: function() {
        // Logic here
    },
    enumerable: false, // <--- Property unreachable through for(k in mc)
    writable: true,    // <-- Optional, default false
    configurable: true // <-- Optional, default false
});