Array sort()

By default, the sort() method puts the items in ascending order. The sort() method calls the String() casting function on every item and then compares the strings. This occurs even if all items in an array are numbers:

 
<!DOCTYPE html>
<html>
<head>
    <title>Example</title>
    <script type="text/javascript">
        var values = [0, 1, 5, 10, 15]; 
        values.sort(); 
        document.writeln(values); //0,1,10,15,5 
       
    </script>
</head>
<body>
</body>
</html>

Click to view the demo

The sort() method can have a comparison function that indicates how to sort.

A comparison function accepts two arguments and returns

a negative number if the first is before the second
a zero if the arguments are equal,
a positive number if the first is after the second.

 
<!DOCTYPE html>
<html>
<head>
    <title>Example</title>
    <script type="text/javascript">
        function compare(value1, value2) { 
            if (value1 < value2) { 
                return -1; 
            } else if (value1 > value2) { 
                return 1; 
            } else { 
                return 0; 
            } 
        } 
        
        var values = [0, 1, 5, 10, 15]; 
        values.sort(compare); 
        document.writeln(values); //0,1,5,10,15 
    </script>
</head>
<body>
</body>
</html>

Click to view the demo

The comparison function could produce results in descending order:

 
<!DOCTYPE html>
<html>
<head>
    <title>Example</title>
    <script type="text/javascript">
        function compare(value1, value2) { 
            if (value1 < value2) {
                return 1;
            } else if (value1 > value2) {
                return -1;
            } else { 
                return 0; 
            } 
        } 
        
        
        var values = [0, 1, 5, 10, 15]; 
        values.sort(compare); 
        document.writeln(values); //15,10,5,1,0 
       
    </script>
</head>
<body>
</body>
</html>

Click to view the demo

sort() returns a reference to the result array.