in javascript, how do you sort a subset of an array?

Question

I have an array and would like to sort all but the last n elements.

For example, if the array is 10 elements long, would like elements 0 through 7 to be sorted while ele

Answer 1

If you need to sort the array in place (i.e. without creating a new, sorted array), which is what the sort() method does, you could do the following:

var array = [5, 2, 6, 4, 0, 1, 9, 3, 8, 7];
var unsorted = array.slice(7);
array.length = 7;
array.sort().push.apply(array, unsorted);

More generally, here's a function to sort a portion of an array in place. Like the sort() method, it also returns a reference to the array.

function partialSort(arr, start, end) {
    var preSorted = arr.slice(0, start), postSorted = arr.slice(end);
    var sorted = arr.slice(start, end).sort();
    arr.length = 0;
    arr.push.apply(arr, preSorted.concat(sorted).concat(postSorted));
    return arr;
}

Example:

var array = [5, 2, 6, 4, 0, 1, 9, 3, 8, 7];
partialSort(array, 0, 7);