CODEWITHSUNDEEP
javascriptstringsortingcompare
Roberto Rizzi
Roberto Rizzi

Reputation: 1543

JavaScript string comparison issue

I'm having an issue with a JavaScript string comparison in a list sorting. It might sound silly but i haven't really found any real solution.

No problem sorting something as below:

A, B, C D ...

Issues come along sorting something like A1, A2, A3, A10, A11 Because it sorts them as following:

A1, A10, A11, A2, A3

I've tried to compare my two strings in 3 different ways.

1)

return a[key].localeCompare(b[key]);

2)

if ( a[key].toString() < b[key].toString() )
  return -1;
if ( a[key].toString() > b[key].toString() )
  return 1;
return 0;

3)

a = a[key].toString(), b = b[key].toString();
for (var i=0,n=Math.max(a.length, b.length); i<n && a.charAt(i) === b.charAt(i); ++i);
if (i === n) return 0;
return a.charAt(i) > b.charAt(i) ? -1 : 1;

Unfortunately, it keeps the wrong sort. Here there's an example where A1 compared with A10 is different than A2 compared with A10, whereas it should be the same.

http://jsfiddle.net/TwCwP/52/

Upvotes: 0

Views: 149

Answers (2)

k0der
k0der

Reputation: 147

As Scott pointed out, the comparison basically happens on binary values. Either follow what Scott suggested or you can try this below code snippet (just added 2 lines to your code to check the length of strings to compare, specific for this scenario)

Note : I haven't tested this piece of code.

if(a[key].length < b[key].length) return -1;
if(a[key].length > b[key].length) return 1;

if ( a[key].toString() < b[key].toString() )
  return -1;
if ( a[key].toString() > b[key].toString() )
  return 1;
return 0;

Or else try formatting your input strings to same length. Eg A02 instead of A2

Upvotes: 0

Scott Hunter
Scott Hunter

Reputation: 49803

You are comparing strings, so they get sorted lexicographically, as if they were words in a dictionary, and not treating the digits as numbers (which is what you seem to want); to do that, you'd need to split the text & numeric portions and convert the latter as actual numbers to compare them.

Upvotes: 1

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