字符串比较在 JavaScript 中是如何工作的？ [复制]

Question

例如，javascript中字符串比较背后的算法是什么

'bc' > 'ac' = true/false ?
'ac' > 'bc' = true/false ?

Answer 1

字符串是逐个字符比较的，所以第一个字母是最重要的，因此

'bc' > 'ac' = true/false ? => true
'ac' > 'bc' = true/false ? => false

如果第一个字母相等，则比较第二个字母，依此类推，直到其中一个大于或小于或等于。

Answer 2

JavaScript 按 Unicode codepoints 的顺序比较字符串，并按字典顺序比较 UTF-16 代码单元。

根据您的问题：

'bc' > 'ac' // Because 'b' comes after 'a'.

Answer 3

这是使用 ECMA-5 中的 The Abstract Relational Comparison Algorithm 计算得出的。下面引用了相关部分。

4. Else, both px and py are Strings
    a) If py is a prefix of px, return false. (A String value p is a prefix 
       of String value q if q can be the result of concatenating p and some
       other String r. Note that any String is a prefix of itself, because 
       r may be the empty String.)
    b) If px is a prefix of py, return true.
    c) Let k be the smallest nonnegative integer such that the character 
       at position k within px is different from the character at position 
       k within py. (There must be such a k, for neither String is a prefix 
       of the other.)
    d) Let m be the integer that is the code unit value for the character 
       at position k within px.
    e) Let n be the integer that is the code unit value for the character 
       at position k within py.
    f) If m < n, return true. Otherwise, return false.

Answer 4

不仅在javascript中，简单来说，所有的字符串比较算法都会遵循字典顺序或字典顺序，这意味着它会逐个字符检查每个字符，如果有些不匹配，你可以决定结果

True: 
ant < any
aaa < aab 
aab < b 
b < baa