How does array.sort work? [duplicate]

Question

Possible Duplicate:
How does Javascript's sort() work?

var myarray=[25, 8, 7, 41]
myarray.sort(function(a,b){return b - a})//  for descending order

In a callback function, what does a and b variables refer to?? why and how does b-a exactly make array in descending order??

Answer 1

a and b are two of the values in the array, that you compare so Javascript can sort them.

The function is called lots of times to determine where each element in the array is compared to all the others. The exact number of times the function is called depends on the number of elements in the array and their original order.

You need to return 0 if the two elements are equal, a negative number if a should be before b and a positive number if b should be before a.

Answer 2

The sort function has internal sorting algorithm. You just provide a way for the algorithm to determine, given two members of the array, which one of them is greater ( that is the purpose of the b-a. ) Using this, the algorithm will be able to place the elements in the necessary order.