NodeJS - Javascript create object instance from String

Question

In my Node.Js application (server side) I have to create an object instance (that is a class, so with new MyClass()) but MyClass is a string.

Its possible to create object instance from a String ? I've see that in browser side I can use window, but here I'm on server side...

I will need this because I will now the name of the class at run time, so I can't instantiate this object in "code".

Moreover, I can have several classes that need to be created in this way. In short, I have a configuration file that explicit this kind of class, and I need to convert this string in a real JavaScript object.

I think that the factory pattern is what you are seeking for: essentialjsdesignpatterns/book/#factorypatternjavascript. — Alberto De Caro
– Alberto De Caro, Commented May 29, 2016 at 9:19
Possible duplicate of How to execute a JavaScript function when I have its name as a string — nwk
– nwk, Commented May 29, 2016 at 9:41

Quentin Roy · Accepted Answer · 2017-04-15 03:19:01Z

14

With nodejs, window is "replaced" by global. So if your class is available in the global context, you can use global["ClassName"] to fetch it.

However, if you can, you may also consider the use of a dictionary of constructors. It is generally cleaner. Here is an example.

var constructors = {
   Class1: Class1,
   Class2: Class2
};

var obj1 = new constructors["Class1"](args);

edited Apr 15, 2017 at 3:19

answered May 29, 2016 at 9:19

Quentin Roy

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1 Comment

Mistre83 Over a year ago

This is exactly what i was in mind! My idea was to create an handler to manage all the classes in a Object like you showed me the factory. But I did not think it was possible to call new on it. You saved my life :D

Jack Wang · Accepted Answer · 2016-05-29 09:22:47Z

1

Do you mean

var myClass = Object.assign(new MyClass(), JSON.parse(classString));

answered May 29, 2016 at 9:22

Jack Wang

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