NFKD 是否通过兼容性和规范等价来分解字符？

Question

在多次尝试理解之后，我得说我不明白 String.prototype.normalize() 是如何工作的。此方法可以采用一些值作为参数：NFC、NFD、NFKC、NFKD.

首先，我不明白 NFD 和 NFKD 之间有什么区别。规范对此非常模糊，所以......在一些 resource 中，我读到 NFD 通过规范等价分解字符。例如：

"â" (U+00E2) -> "a" (U+0061) + " ̂" (U+0302)

和NFKD通过兼容性分解字符。例如：

"ﬁ" (U+FB01) -> "f" (U+0066) + "i" (U+0069)

但事实并非如此。 NFKD不仅通过兼容性分解字符。它也可以完美地处理第一个例子：

let s = `\u00E2`; //"â" 
console.log(s.normalize('NFD').length); //2
console.log(s.normalize('NFKD').length); //2

是否意味着NFKD可以通过兼容性和规范等价来分解字符？ NFD 仅通过规范等价分解字符...?

let s = `\uFB01`; //"ﬁ"
console.log(s.normalize('NFD').length); //1

Answer 1

Unicode

The type of full decomposition chosen depends on which Unicode Normalization Form is involved. For NFC or NFD, one does a full canonical decomposition, which makes use of only canonical Decomposition_Mapping values. For NFKC or NFKD, one does a full compatibility decomposition, which makes use of canonical and compatibility Decomposition_Mapping values.

这就是 NFC/NFD 和 NFKC/NFKD 如此工作的原因：

let s1 = '\uFB00'; //"ﬀ"
let s2 = '\u0066\u0066'; //"ff"
console.log(s1.normalize('NFD').length); //doesn't work with compatible -- only can. eq.

let t1 = `\u00F4`; //ô
let t2 = `\u006F\u0302`; //ô
console.log(t1.normalize('NFKD').length); //also works with can. eq.
console.log(t2.normalize('NFKC').length); //also works with can. eq.

这是完全可以理解的，因为...

MDN

All canonically equivalent sequences are also compatible, but not vice versa.

NFKD 是否通过兼容性和规范等价来分解字符？

Does NFKD decompose characters by compatibility and also canonical equivalence?

javascript

unicode

normalize