问题
I'm trying to use JavaScript's localeCompare function for sorting strings.
I was surprised by the results of running the following lines in the devTools console:
"a".localeCompare("b") // returns: -1
"A".localeCompare("b") // returns: -1
Another test:
"b".localeCompare("a") // returns: 1
"B".localeCompare("a") // returns: 1
Even when I am more specific about my sort I get the same result:
"a".localeCompare("b", { usage: "sort", sensitivity: 'variant' }) // -1
"A".localeCompare("b", { usage: "sort", sensitivity: 'variant' }) // -1
"b".localeCompare("a", { usage: "sort", sensitivity: 'variant' }) // 1
"B".localeCompare("a", { usage: "sort", sensitivity: 'variant' }) // 1
I want to use localeCompare to compare strings in a case-sensitive way, so shouldn't "b" compared to "a" and "B" compared to "a" have opposite results?
回答1:
LocalCompare can be case-sensitiv, enabled by { sensitivity: 'case'} or the unicode extension: u-kf-upper or u-kf-lower.
The spec of LocalCompare says, that:
The result is intended to order String values in the sort order specified by the system default locale
Or the locale you can add as argument.
The default for en-US for the case sensitive order is "lower" with:
aAbBcC ...
You could change it to "upper", which is:
AaBbCc ...
This test shows that switching from upper to lower does only affect the same letter, and does not sort uppercase-alphabet before lowercase or visa versa.
var b = "A".localeCompare("a", 'en-US-u-kf-lower'); // 1
var c = "A".localeCompare("a", 'en-US-u-kf-upper'); // -1
var d = "A".localeCompare("b", 'en-US-u-kf-upper'); // -1
var e = "A".localeCompare("b", 'en-US-u-kf-lower'); // -1
- There might be a locale that sorts uppercase/lowercase differently, but I'm not aware of any...
- the international sort order is case insensitive
- ASCII sort order would be
ACb - Some locales have different orders: Finnish for example treads V like W:
Va Wb Vc...
Does case-sensitivity affect numeric values in any way?
var b = "1".localeCompare("a", 'en-US-u-kf-lower'); // -1
var c = "1".localeCompare("A", 'en-US-u-kf-upper'); // -1
var d = "104".localeCompare("a", 'en-US-u-kf-upper'); // -1
no, but ...
there is an option, how numeric values can be compared: kn
with the option or Unicode extension kn one can enable numeric comparison (kn-true):
var b = "10".localeCompare("2", 'en-US-u-kn-true'); // 1
var c = "10".localeCompare("2", 'en-US'); // -1
However, numbers are always before letters:
var d = "1".localeCompare("a", 'en-US-u-kn-true'); // -1
var e = "1".localeCompare("a", 'en-US'); // -1
来源：https://stackoverflow.com/questions/34861386/force-localecompare-to-be-case-sensitive