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JavaScript

Jack Hou
Jack Hou
6,975 Points

Methods Part 2 lecture

in this lecture, Jim went over something like my_array.sort(function( a , b ) ) { return a - b; }

in order to sort the array in numeric order. I have no idea what the above is doing, and the function makes no sense to me. Can someone provide a detail explanation on what Jim is doing here and why it helps to sort the array in order?

1 Answer

The anonymous function inside the sort method (in this case, function(a,b) ) takes 2 parameters (a & b). Since you're performing this method on "my_array", it's going to automatically grab 2 values from the array to compare against each other.

The sorting happens at the return (a-b) line. There are 3 possible results to this statement:

  • Less than 0: Sort "a" to be a lower index than "b"
  • Zero: "a" and "b" should be considered equal, and no sorting performed.
  • Greater than 0: Sort "b" to be a lower index than "a".

Quick example: var myarray=[18, 8, 7, 45] myarray.sort(function(a,b){return a - b})

The first time through, the sort function might compare 18 & 8. Since the resulting number of "a-b" (18-8) is a positive number, the return(a-b) statement will send back >0. When the sort function compares 7 & 45, though, it will return a negative number, so the statement will return <0.

Jack Hou
Jack Hou
6,975 Points

are the two numbers grabbed by a and b random?