Returns the index within this string of the last occurrence of
the specified character, searching backward starting at the
specified index. For values of
ch in the range
from 0 to 0xFFFF (inclusive), the index returned is the largest
value k such that:
is true. For other values of(this.charAt(k) == ch) && (k <= fromIndex)
ch, it is the largest value k such that:
is true. In either case, if no such character occurs in this string at or before position(this.codePointAt(k) == ch) && (k <= fromIndex)
All indices are specified in
(Unicode code units).
|a character (Unicode code point).|
| the index to start the search from. There is no
restriction on the value of |
if the character does not occur before that point.