How does string comparison work in JavaScript?
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.