JavaScript sort function always sorts by ascending order, NOT descending
Hello.
I am trying to allow ascending or descending sorting using the sort function, but my list ALWAYS comes up in ascending order. I've thrown together a sample program (below) exemplifying my problem. What am I doing wrong? (I'm a newbie and just starting to learn JavaScript.)
It looks as if my SortIt function always returns the wrong value.
Thanks in advance.
-Brian
<html>
<head>
<script language = "JavaScript">
<!--
var InputText = prompt ('Enter a text string below:', ' ');
var Word = InputText.split (" ")
var OrderType = prompt ('Enter order type ("ascending" or "descending"):');
function SortIt (a, b){
RetValue = 0
if (a < b)
RetValue = -1
else
if (a > b)
RetValue = 1
return RetValue;
}
//-->
</script>
</head>
<body>
<script language = "JavaScript">
<!--
document.writeln ("Original:<br>");
for (i = 0; i < Word.length; i++)
document.writeln (Word[i] + '<br>');
Word.sort (SortIt);
document.writeln ("<br>Sorted:<br>");
for (i = 0; i < Word.length; i++)
document.writeln (Word[i] + '<br>');
//-->
</script>
</body>
</html>
I am trying to allow ascending or descending sorting using the sort function, but my list ALWAYS comes up in ascending order. I've thrown together a sample program (below) exemplifying my problem. What am I doing wrong? (I'm a newbie and just starting to learn JavaScript.)
It looks as if my SortIt function always returns the wrong value.
Thanks in advance.
-Brian
<html>
<head>
<script language = "JavaScript">
<!--
var InputText = prompt ('Enter a text string below:', ' ');
var Word = InputText.split (" ")
var OrderType = prompt ('Enter order type ("ascending" or "descending"):');
function SortIt (a, b){
RetValue = 0
if (a < b)
RetValue = -1
else
if (a > b)
RetValue = 1
return RetValue;
}
//-->
</script>
</head>
<body>
<script language = "JavaScript">
<!--
document.writeln ("Original:<br>");
for (i = 0; i < Word.length; i++)
document.writeln (Word[i] + '<br>');
Word.sort (SortIt);
document.writeln ("<br>Sorted:<br>");
for (i = 0; i < Word.length; i++)
document.writeln (Word[i] + '<br>');
//-->
</script>
</body>
</html>
ASKER CERTIFIED SOLUTION
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a=a+"b":
a=a+"" is there to convert it to a string. If it's considered to be a number by Javascript, the toLowerCase() function will fail.
if(OrderType=='descending'
the sortIt() compares two items from your array, and set RetValue to -1 if "a" is less than "b" and 1 if "a" is higher than "b". That's why use this line:
if(OrderType=='descending'
to return the oposite result from the function if you're sorting the items in descending order.
If you use
if(OrderType=='descending'
and a is less than b, it won't return the value in oposite order, since RetValue allready is -1 from the test above.
Example: The two words "Is" and "This" is sent to the function
a = "is",
b = "This"
This part of your function:
if (a < b)
RetValue = -1
else
if (a > b)
RetValue = 1
set RetValue to -1 since "is" is smaller than "This". If you now uses the the line
if(OrderType=='descending'
RetValue will still be -1 and not the oposite which is 1. That's why I used
if(OrderType=='descending'
Hope it makes sense. It's not so easy to explain:-)
Batalf
a=a+"" is there to convert it to a string. If it's considered to be a number by Javascript, the toLowerCase() function will fail.
if(OrderType=='descending'
the sortIt() compares two items from your array, and set RetValue to -1 if "a" is less than "b" and 1 if "a" is higher than "b". That's why use this line:
if(OrderType=='descending'
to return the oposite result from the function if you're sorting the items in descending order.
If you use
if(OrderType=='descending'
and a is less than b, it won't return the value in oposite order, since RetValue allready is -1 from the test above.
Example: The two words "Is" and "This" is sent to the function
a = "is",
b = "This"
This part of your function:
if (a < b)
RetValue = -1
else
if (a > b)
RetValue = 1
set RetValue to -1 since "is" is smaller than "This". If you now uses the the line
if(OrderType=='descending'
RetValue will still be -1 and not the oposite which is 1. That's why I used
if(OrderType=='descending'
Hope it makes sense. It's not so easy to explain:-)
Batalf
ASKER
That is great, Batalf. Thanks so much!
Glad I could help! Thanks for the points
Batalf
Batalf
ASKER
Can you explain a couple of things to me... Why are you doing this: a=a+"" ?
Also, instead of this:
if(OrderType=='descending'
why didn't you say this:
if(OrderType=='descending'
Aren't they the same thing?