up vote 2 down vote favorite
1

My array isn't being sorted properly. Can someone let me know what I am doing wrong?

...
 sortArray = new Array ("hello", "Link to Google", "zFile", "aFile");

//sort array
        if (dir == "asc") { 
            sortArray.sort(function(a,b){return a - b}); 
        } else { 
            sortArray.sort(function(a,b){return b - a});
        }

        for(var i=0; i<sortArray.length; i++) { 
            console.log(sortArray[i]);
        }

the log is showing them in the same order as they were entered.

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66% accept rate
@Tim Cooper's answer is the only one you need. – Brian Driscoll Mar 29 '11 at 17:54
of course you can also do this handy little shortcut .......................................................... (sortArray.sort())[(dir === 'asc' ? 'reverse' : 'slice' )]() – qwertymk Mar 29 '11 at 18:27
@mVChr: DEMO – qwertymk Mar 29 '11 at 18:34
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4 Answers

up vote 8 down vote accepted

You want to make a comparison in your sort, not a subtraction:

if (dir == "asc") {
    sortArray.sort(function(a, b) {
        return a.toLowerCase() > b.toLowerCase()
    });
} else {
    sortArray.sort(function(a, b) {
        return b.toLowerCase() > a.toLowerCase()
    });
}

I also used toLowerCase() so that 'Link to Google' is placed appropriately.

See example →

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I accepted yours for the toLowerCase() add on...though everyone deserves a +1. – PruitIgoe Mar 29 '11 at 18:11
This answer does not seem to work in Chrome. The comparator function is supposed to return 0 if a and b are equal, a positive integer if a should be sorted to a higher index than b, and a negative integer if a should be sorted to a lower index than b. – Mike Sep 16 at 20:38
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up vote 3 down vote

Your comparator functions returns NaN, since it receives two strings, and performs subtraction, an operation that isn't well-defined on strings.

What you should have is something more like:

function(a,b){
   return a>b? 1 : (a<b ? -1 : 0);
}

or you can use localeCompare:

function(a,b){
   return a.localeCompare(b);
}

Remember to treat case appropriately, e.g. "L" < "a" whilst "l" > "a"

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up vote 4 down vote

The trouble is that "a - b" is treating the strings like numbers, which returns NaN. You will get the behavior you are looking for (assuming you are looking for case-sensitive sorts) if you replace your sorts with:

    if (dir == "asc") { 
        sortArray.sort(function(a,b){return a < b ? -1 : 1}); 
    } else { 
        sortArray.sort(function(a,b){return b < a ? -1 : 1});
    }
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up vote 6 down vote

You're trying to sort by subtracting strings, to which you'll get NaN.

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Thanks everyone, obviously I misread the docs on that one - : D – PruitIgoe Mar 29 '11 at 18:10
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