Can new be applied to any function in JavaScript? [duplicate]

Question

Many sources like MDN and this tutorial define a concept called "constructor" that should be used with the new keyword to create an instance in traditional OOP's sense. But what "constructor" means is not formally stated.

It seems to me that literally any function can be used with new. (Though function without any manipulation to this in its definition is not particularly useful when newed, because it merely returns an empty object). Is this correct?

yes, we can apply a new on a function, and it is not always empty, it can have variables, it can also be a closure, in JS everything is object, even the functions — Mister Jojo
– Mister Jojo, Commented Apr 16, 2021 at 2:07
No, there are some functions that will throw when you try to use new on them. — Bergi
– Bergi, Commented Apr 16, 2021 at 2:15
Have a look at the answers to How to check if a Javascript function is a constructor, Are there any JS objects for which IsCallable is false but IsConstructor is true? and maybe JavaScript: Are all Standard Built-In Objects actually constructor functions? for the technical details — Bergi
– Bergi, Commented Apr 16, 2021 at 2:25
@wlnirvana Arrow functions, class methods, many builtins, and of course function Example() { if (new.target) throw new TypeError("Don't new() me!"); } :-) — Bergi
– Bergi, Commented Apr 16, 2021 at 2:26

narojo · Accepted Answer · 2021-04-16 04:45:52Z

-1

When you use the new keyword, it creates a new object. When you create an instance of a class with new, it creates an object, and any properties in the constructor method will be initialized in the object as well.

answered Apr 16, 2021 at 4:45

narojo

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