How many intricate objects are instantiated in memory when running the code snippet provided above?

When looking at the given code, how many complex objects can we identify in memory?

function Foo() {
  this.one = function() {
    return "one";
  }
}

var f = new Foo();    

Foo.two = function() {
  return "two";
};

Here's what I see:

  1. The Foo constructor function object
  2. The instance of Foo constructor function object under f.__proto__
  3. The object f itself
  4. An object for the one function
  5. An object for the two function

Answer №1

This particular question poses a challenge as the specification neglects to address objects created in memory.

JavaScript boasts a variety of implementations, such as v8 in Chrome, JSC in Safari, SpiderMonkey in Firefox, JScript and Chakra in IE, Rhino serving as a scripting engine in Java, among others. Additionally, there are more obscure implementations available.

To complicate matters further, the implementation does delineate elements like a VariableEnvironment of the function, emphasizing that it's not simply an implementation detail but rather a tool for interpretation to enhance the readability of the specification.

With the presented code - a "clever" engine could potentially allocate zero objects in this scenario.

Why is this so? The above code lacks any side effects. There is no invocation of Foo or utilization of f anywhere, rendering it essentially 'dead code' due to non-utilization.


Despite that factor, aside from the minor noted issue - several variables may be allocated depending on how the code is employed: Notably, the strings "foo" and "one" might require allocation (as they're primitive, but boxing may be necessary based on usage).

Alternatively, the engine has the option to inline these functions entirely. If this approach is taken, one and two would be directly inlined without needing separate allocations.

As a result, providing an accurate answer to this query proves to be highly challenging :)

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