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Hello I have a textbox having values like 

<input type="hidden" value="2,1,4,5,3,6,7,8,9,10,11,12" class="sortvalues" id="1_1_parent">

Now what I want to take the value of this textbox, want to split the values to array and then as last result I need a sorted array.

What I have done. 

 allsortedValues =  $(".sortvalues").val();
 allsortedValues = allsortedValues.split(",");
 allsortedValues = allsortedValues.sort();

When I check the array 

 console.log(allsortedValues);

It shows 

  1,10,11,12,2,3,4,5,6,7,8,9

Sorting array as 1, 10, 11, 12, 2.....

I have even used

allsortedValues = allsortedValues.split(",").map(function(x){return parseInt(x)});

before applying sort and in other case I have even used parseInt like

for(var i = 0; i < allsortedValues.length; i++) {

   allsortedValues[i] = parseInt(allsortedValues[i]);
}

before applying sort but in all cases result is same. Will some one guide what am I doing wrong?

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  • 4
    stackoverflow.com/questions/1063007/… It is possible duplicated Commented Apr 2, 2013 at 13:23
  • Your sort is working fine, javascript is treating your input as strings instead of numbers hence the unexpected behavior. See @Pointy's answer for a proper solution. Commented Apr 2, 2013 at 13:26

2 Answers 2

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26

You'll have to pass in a comparator function that converts the strings to numbers:

allsortedvalues = allsortedvalues.sort(function(a,b) {
  return (+a) - (+b);
});

If there's a chance that some of your array entries aren't nicely-formatted numbers, then your comparator would have to get more complicated.

The construction (+a) involves the unary + operator, which doesn't do anything if a is already a number. However if a is not a number, the result of +a will be either the value of a when interpreted as a number, or else NaN. A string is interpreted as a number in the obvious way, by being examined and parsed as a string representation of a number. A boolean value would be converted as false -> 0 and true -> 1. The value null becomes 0, and undefined is NaN. Finally, an object reference is interpreted as a number via a call to its valueOf() function, or else NaN if that doesn't help.

It's equivalent to use the Number constructor, as in Number(a), if you like. It does exactly the same thing as +a. I'm a lazy typist.

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7 Comments

I guess the (+a) stuff might not be strictly necessary, but I find it nice to highlight what's going on a little.
(+)'ses look quite confusing. I'd suggest Number(a)-Number(b) if you want to be explicit.
@thg435 agree, I prefer human language :)
Personally I think just return a - b;//compare two numbers with a comment is clear enough.
@Pointy just want to comment, for a lazy typist, you sure are not lazy to type all those epxlanation about +a being equivalent to Number(a). If you use Number(a) in your code, you don't need to explain that much :)
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If compareFunction is not supplied, elements are sorted by converting them to strings and comparing strings in lexicographic ("dictionary" or "telephone book," not numerical) order. For example, "80" comes before "9" in lexicographic order, but in a numeric sort 9 comes before 80.

To compare numbers instead of strings, the compare function can simply subtract b from a:

function compareNumbers(a, b)
{
  return a - b;
}

https://developer.mozilla.org/en-US/docs/JavaScript/Reference/Global_Objects/Array/sort

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1 Comment

Erm, I answered the actual question: "Javascript not sorting correctly, what am I doing wrong?" That doesn't necessitate providing the correct sorting function. That is in the linked documentation, which the OP clearly should read.

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