Say I have the following code - and by "I" I mean that its not my code and I cannot remove the new operation. I only received the instance of foo after its instantiated.
var foo = new function() {
this.bar = 'baz';
}
Is it possible to get the original function and effectively perform another new on it? If so, are there cases where it would not be a clean clone?
var secondFoo = ...foo...
secondFoo.bar = 'qux';
foo.bar // 'bad'
secondFoo.bar // 'qux'
You can, objects expose their constructor in the constructor property:
a = new function(){ this.foo = Math.random()}
>> Object {foo: 0.11541059240698814}
a.constructor
>> function(){ this.foo = Math.random()}
b = new a.constructor
>> Object {foo: 0.867641115328297}
But most likely, you wouldn't want to.
Constructors are blue prints for creating new instances. Its not idiomatic to pull from an instantiated object over calling the constructor itself.
Object.getPrototypeOf( b ).x = 'lol'; a.x === 'lol';. Of course you can't modify a's foo like that (you can't modify any of a's direct properties through b), only new properties, or ones that end up getting deleted from a will be visible through the prototype chain.Remove the new operator.
var foo = function() {
this.bar = 'baz';
}
You can now instantiate new objects from the constructor foo.
var instance1 = new foo();
var instance2 = new foo();
instance1.bar = 'test';
console.log(instance1.bar); // 'test'
console.log(instance2.bar); // 'baz'
foo.