I was checking this question Javascript Deep Comparison
The solution of the question asker did not convince me so I tried to analyze the problem and came up with that

var obj = {here: 2};

console.log(deepEqual(obj, obj));

// → true

console.log(deepEqual(obj, {here: 1}));

// → false

console.log(deepEqual(obj, {here: 2}));

// → true

function deepEqual(a,b)

{

  if( (typeof a == 'object' && a != null) &&

      (typeof b == 'object' && b != null) )

  {

     var count = [0,0];

     for( var key in a) count[0]++;

     for( var key in b) count[1]++;

     if( count[0]-count[1] != 0) {console.log('1');return false;}

     for( var key in a)

     {

       if(!(key in b) || !deepEqual(a[key],b[key])) {console.log('2');return false;}

     }

     for( var key in b)

     {

       if(!(key in a) || !deepEqual(b[key],a[key])) {console.log('3');return false;}

     }  

  }

  console.log('a:'+a+' b:'+b);

  return a===b;

}

obj === { here:2 }

This code fails the last test ( console.log(deepEqual(obj, {here: 2})) ) but the logic of considering objects deeply equal if they have respectively equal keys and values despite being different instances in memory does not convince me. Is there's a problem with my 'solution' or the mistake lies in the presumptions of the exercise? Is the code mentioned in the question I linked valid?

Resources that hikinthru forgot to mention ( http://eloquentjavascript.net/04_data.html#exercise_deep_compare )