# JavaScript: DHTML Quick Sort

This page demonstrates the Quick Sort algorithm. This is the most advanced algorithm of the four presented, but has some problems w.r.t. speed and the fact that it is not a 'stable' sort (see link at bottom of page for details). At this stage we've found the Shell Sort algorithm to be more efficient with web data.

idcolourrandom
1orange281
2blue652
3orange581
4yellow419
5orange146
6blue192
7orange197
8orange757
9blue450
10purple449
11green11
12green809
13orange653
14orange70
15green466
16orange826
17yellow928
18green736
19yellow100
20green800
Sort by DESC?

## How does it work?

For a more detailed discussion on the sorting process, you can refer to the Bubble Sort page. The only difference between the two is the actual sorting algorithm, with the Quick Sort, in theory, being much faster:

``` // global variables var col = 0; var parent = null; var items = new Array(); var N = 0; function quicksort(m, n, desc) { if(n <= m+1) return; if((n - m) == 2) { if(compare(get(n-1), get(m), desc)) exchange(n-1, m); return; } i = m + 1; j = n - 1; if(compare(get(m), get(i), desc)) exchange(i, m); if(compare(get(j), get(m), desc)) exchange(m, j); if(compare(get(m), get(i), desc)) exchange(i, m); pivot = get(m); while(true) { j--; while(compare(pivot, get(j), desc)) j--; i++; while(compare(get(i), pivot, desc)) i++; if(j <= i) break; exchange(i, j); } exchange(m, j); if((j-m) < (n-j)) { quicksort(m, j, desc); quicksort(j+1, n, desc); } else { quicksort(j+1, n, desc); quicksort(m, j, desc); } } function sortTable(tableid, n, desc) { parent = document.getElementById(tableid); col = n; if(parent.nodeName != "TBODY") parent = parent.getElementsByTagName("TBODY"); if(parent.nodeName != "TBODY") return false; items = parent.getElementsByTagName("TR"); N = items.length; // quick sort quicksort(0, N, desc); }```

expand code box

This algorithm makes use of the get and compare function presented previously in the Bubble Sort demonstration, and the exchange function introduced in the Shell Sort demonstration.

The sorting functions presented so far have all been quite inefficient because they first have to read the DOM and then apply the various algorithms. To get around this limitation, each of the sorting algorithms has also been implemented using object-oriented (OOP) techniques.

All four methods (using OOP) are now available as external javascript files on the related page: DHTML Sorting Using OOP.

## References

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