从对象中删除对象？

Question

Given something like this:

function test(){
   var o = {
      // ...
      del: function(){}
   }
   return o;
}

Is it possible to have .del() remove/set to null the reference to the variable o such that it becomes eligible for garbage collection?

In other words, is this possible (and if so how):

var test1 = test();
// test1 = {...}
test1.del();
// test1 == null or test1 == undefined;

I did try setting o = null but the outside reference ( test1 would still refer to the object). I also understand that setting test1 = null would solve the issue, but where's the fun in that?

Answer 1

Based on what I see in the comments, this pattern wouldn't do what you need. You are returning a new instance of an object every time the test function is called or "newed" up. It is up to the caller of the function to clean up it's new instance of "o". On this train of thought, you shouldn't have to explicitly set a value to null or undefined to make it eligible for garbage collection. Once there are no more references to an object, it will be cleaned up for you.

Here is a great example from MDN-

function f(){
  var o = {};
  var o2 = {};
  o.a = o2; // o references o2
  o2.a = o; // o2 references o

  return "azerty";
}

f();

The internal scope of f() will be cleaned up after the function returns, since the variables inside are not "reachable" anymore. It's called the Mark and Sweep algorithm.

Answer 2

No it would not be possible to have a method del() that would let an object be garbage collected. For the garbage collector to kick in, the object must be unreachable, as you had in your post test1 = null;

The purpose of garbage collection is so you don't have to worry about managing your memory.