Passing variable by full reference

Question

I want to pass an object or array to a function, make it undefined, and see the changes after the function execution ends.

var arr = [\'aaa\', \'bbb\', \'ccc\'];         


        

Answer 1

JavaScript is a pass by value language, so modifying the value of a function parameter inside the function cannot have an effect on the variable passed as the argument.

If you want to do something like that, you can have your function return the value:

var reset = function(param) {
  // think think think
  if (whatever)
    return undefined;
  return param;
};

arr = reset(arr);

Now, if the function decides that the right thing to do is empty out the source variable, it returns undefined.

If you just want to clear the variable, however, there's no need for a function:

arr = undefined;

Answer 2

You can't pass a variable by reference in JavaScript. What you can do instead, if the variable is in the same or greater scope than reset(), is use the variable itself inside the function as shown below:

var
  arr = ['aaa', 'bbb', 'ccc'],
  reset = function () {
    arr = undefined;
  }

reset();
console.log(arr);

Or instead you can just make it equal to undefined:

var arr = ['aaa', 'bbb', 'ccc'];
arr = undefined;
console.log(arr);