Can you alter a Javascript function after declaring it?

Question

Let\'s say I have var a = function() { return 1; }. Is it possible to alter a so that a() returns 2? Perhaps by editing a

Answer 1

So you want to modify the code of a function directly, in place, and not just reassign a different function to an existing variable.

I hate to say it, but as far as I have been able to figure it out - and I have tried -, it can't be done. True, a function is an object, and as such it has methods and properties which can be tweaked and overwritten on the object itself. Unfortunately, the function body is not one of them. It is not assigned to a public property.

The documentation on MDN lists the properties and methods of the function object. None of them gives us the opportunity to manipulate the function body from the outside.

That's because according to the spec, the function body is stored in the internal [[Code]] property of the function object, which can't be accessed directly.