Issue 103: javascript Array.sort() bug
http://code.google.com/p/v8/issues/detail?id=103
Comment #2 by [EMAIL PROTECTED]:
It is, sortof, expected behavior - in the sense that the behavior of sort
with this
comparison function is undefined.
A comparison function for sort, given arguments a and b, must return a
positive
number if a > b, a negative number if a < b, and zero if they are equal.
See "consistent comparison function", ECMA 262,3ed, section 15.4.4.11, which
also states:
"If comparefn is not undefined and is not a consistent comparison
function for the
elements of this array (see below), the behaviour of sort is
implementation-
defined."
This comparison function returns true or false. When converted to a number,
true
becomes 1 and false become 0. That is, if a <= b, the sort operation
considers them
equal. The problem is that the function is not symmetric: The arguments
(50,60)
returns false, which is interpreted as 50 being equal to 60, but passed as
(60,50) it
returns true, meaning that 60 > 50.
I.e., it's a coincidence that it works anywhere (except perhaps Firefox,
which does
seem to work consistently). The comparison function is not satisfying the
contract
expected by the sort function, so whether it works or not depends entirely
on the
order of arguments that the sort routing gives to the comparison.
This example only appears to work in IE, because the initial array is
already sorted.
If you start out with an unsorted array, it doesn't sort at all:
["100", "50", "60"].sort(function(a,b) {return Number(a)>Number(b)})
yields [100,50,60] in IE. Opera does the same. Firefox *does* sort, though.
For a better comparison function, try:
function cmp(a,b) { return a == b ? 0 : a < b ? -1 : 1; }
function numberCmp(a,b) { return cmp(Number(a),Number(b)); }
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