Ordering a Multi-Dimensional Array with Letters and Numbers

Question

My school has asked me to develop a web app that can record homework, show timetables, etc. I use localStorage objects to store each homework, and then they are retrieved and put into a multi-dimensional array.

I have an Array that looks like this: (Placeholders for title, etc. used!)

1hvfkjdvhjh463574hdv
   0 : history
   1 : title
   2 : description
   3 : setdate
   4 : duedate
   5 : importance

1hft6ry4uyguy
   0 : art
   1 : title
   2 : description
   3 : setdate
   4 : duedate
   5 : importance

1ehfhhrewvfbjvds63
   0 : geography
   1 : title
   2 : description
   3 : setdate
   4 : duedate
   5 : importance

The 1 followed by random characters represents the category of the localStorage object (1 for homework - as oppose to timetable, etc.) and a unique 'id' for the homework.

Everything works fine apart from sorting/ordering the array.

The below method does not seem to work:

homework.sort(function(a, b) {
    if (a[0] < b[0]) return  1;
    if (a[0] > b[0]) return -1;
    return 0;
});

for(var x in homework) {
    document.write(homework[x] + "<br />");
}

The desired effect is that in the for loop, the array is ordered by the lesson, Art, History, Geography...

Answer 1

In your comment you said

var i = 0, oJson = {}, sKey;
homework = new Array();
for (;sKey = window.localStorage.key(i); i++) {
    oJson[sKey] = JSON.parse(window.localStorage.getItem(sKey));
    if(sKey.substring(0,1) === "1") { homework[sKey] = oJson[sKey]; }
}

Using homework[sKey] means you are adding properties to the Array as if it's an Object, not adding new items to your Array like it's a list. You can't sort these properties.

Try creating homework to have items in the form [sKey, oJson[sKey]] instead.

var i = 0, oJson = {}, sKey,
    homework = [];                             // Array literal
while (sKey = window.localStorage.key(i++)) {  // same loop using while
    oJson[sKey] = JSON.parse(window.localStorage.getItem(sKey));
    if(sKey.charAt(0) === "1")                 // test first char
        homework.push([sKey, oJson[sKey]]);    // Using `homework` as Array
}

Now when you sort your array items, you'll want to sort by the first index, just as you were trying to before.