How does string comparison work in JavaScript?

Question

What the algorithm work behind string comparison in javascript, for example

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

Strings are compared alphabetically. `b` is greater than `a` etc. — Jozef Chocholacek, Jul 21 '16 at 07:55
Does this answer your question? [Why is one string greater than the other when comparing strings in JavaScript?](https://stackoverflow.com/questions/7087811/why-is-one-string-greater-than-the-other-when-comparing-strings-in-javascript) — customcommander, Nov 22 '20 at 00:04

score 4 · Accepted Answer · answered Jul 21 '16 at 08:19

This is calculated using The Abstract Relational Comparison Algorithm in ECMA-5. The relevant part is quoted below.

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.

score 1 · Answer 2 · edited Nov 29 '20 at 11:03

1

JavaScript compares strings by the order of Unicode codepoints and lexicographically compares UTF-16 code units.

From your question:

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

edited Nov 29 '20 at 11:03

Sebastian Simon

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answered Jul 21 '16 at 07:57

Alongkorn

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score 1 · Answer 3 · answered Jul 21 '16 at 09:25

Not only in javascript , In simple, all string comparison algorithm will follow the lexicographical order or dictionary order, which means it will check each character by character, if some mismatches, you can decide the result

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

score 0 · Answer 4 · answered Jul 21 '16 at 07:56

Strings are compared character by character, so the very first letter is the most significant, hence

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

if the first letter will be equal then, second will be compared and so on, till one of them will be greater or less or equal.

How does string comparison work in JavaScript?

4 Answers4

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