6.11. Implementing a Custom Sort


You want to sort an array in a way such that the basic sort( ) and sortOn( ) methods do not suffice. You want to sort an array in a case-insensitive manner, perform a numeric sort, or use another custom or multikey criterion.


Use the sort( ) method and pass it a reference to a compare function.


If you want complete control over sorting criteria, use the sort( ) method with a custom compare function (also called a sorter function). The compare function is called repeatedly by the sort( ) method to reorder two elements of the array at a time. The compare function receives two parameters (let’s call them a and b), which it should compare to determine which one should be ordered first. Your custom compare function should return a positive number, a negative number, or 0, depending on how the elements are to be sorted. If the function returns a negative number, a is ordered before b. If the function returns 0, then the current order is preserved. If the function returns a positive number, a is ordered after b. Your compare function is called with every relevant combination of elements until the entire array has been properly ordered. Using a custom compare function is easier than it sounds. You do not need to concern yourself with the details of the sorting algorithm; you simply specify the criteria for comparing any two elements.

Here is a simple compare function that performs a case-insensitive sort:

function insensitiveSorter(a, ...

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