UP-FRONT NOTE: I am not using jQuery or another library here because I want to understand what I’ve written and why it works (or doesn’t), so please don’t answer this with libraries or plugins for libraries. I have nothing against libraries, but for this project they’re inimical to my programming goals.
That said…
Over at http://meyerweb.com/eric/css/colors/ I added some column sorting using DOM functions I wrote myself. The problem is that while it works great for, say, the simple case of alphabetizing strings, the results are inconsistent across browsers when I try to sort on multiple numeric terms—in effect, when I try to do a sort with two subsorts.
For example, if you click “Decimal RGB” a few times in Safari or Firefox on OS X, you get the results I intended. Do the same in Chrome or Opera (again, OS X) and you get very different results. Yes, Safari and Chrome diverge here.
Here’s a snippet of the JS I’m using for the RGB sort:
sorter.sort(function(a,b){
return a.blue - b.blue;
});
sorter.sort(function(a,b){
return a.green - b.green;
});
sorter.sort(function(a,b){
return a.red - b.red;
});
(sorter
being the array I’m trying to sort.)
The sort is done in the tradition of another StackOverflow question “How does one sort a multi dimensional array by multiple columns in JavaScript?” and its top answer. Yet the results are not what I expected in two of the four browsers I initially tried out.
I sort (ha!) of get that this has to do with array sorts being “unstable”—no argument here!—but what I don’t know is how to overcome it in a consistent, reliable manner. I could really use some help both understanding the problem and seeing the solution, or at least a generic description of the solution.
I realize there are probably six million ways to optimize the rest of the JS (yes, I used a global). I’m still a JS novice and trying to correct that through practice. Right now, it’s array sorting that’s got me confused, and I could use some help with that piece of the script before moving on to cleaning up the code elsewhere. Thanks in advance!
UPDATE
In addition to the great explanations and suggestions below, I got a line on an even more compact solution:
function rgbSort(a,b) {
return (a.red - b.red || a.green - b.green || a.blue - b.blue);
}
Even though I don’t quite understand it yet, I think I’m beginning to grasp its outlines and it’s what I’m using now. Thanks to everyone for your help!