An Object Null And { } Behaviour In Javascript

Program1 var ninja = { yell: function(n){ return n > 0 ? ninja.yell(n-1) + 'a' : 'hiy'; } }; assert( ninja.yell(4) == 'hiyaaaa', 'A single object isn't too bad, eit

Solution 1:

This has nothing to do with the difference between null and {}, it depends only on how the ninja.yell function is defined.

The first example doesn't work because inside the ninja.yell function, you are referring to ninja again:

return n > 0 ? ninja.yell(n-1) + "a" : "hiy"; 

So, if later on your are assigning null to ninja, this code will throw an error because null doesn't have a property yell.

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The second example works because that's what you are exactly not doing. Instead of referring to the object that holds the function (ninja), you are giving the function a name and directly refer to that name:

function yell(n){ 
   return n > 0 ? yell(n-1) + "a" : "hiy"; 
} 

The function is basically "self-contained", it doesn't depend on the values of free variables.

Solution 2:

variables are references. so in the first one, yes, ninja.yell already assigned before ninja=null, but samurai.yell is a reference to ninja.yell - it is pointing to ninja.yell.

if you then later set ninja to null, samurai.yell, which is pointing to ninja, will also be null

Solution 3:

Have a look at this. It may help you out (the title of the question is not accurate though): Allocate memory in JavaScript