The charCodeAt() method returns an integer between 0 and 65535 representing the UTF-16 code unit at the given index (the UTF-16 code unit matches the Unicode code point for code points representable in a single UTF-16 code unit, but might also be the first code unit of a surrogate pair for code points not representable in a single UTF-16 code unit, e.g. Unicode code points > 0x10000). If you want the entire code point value, use codePointAt().
The indexOf() method returns the index within the calling String object of the first occurrence of the specified value, starting the search at fromIndex. Returns -1 if the value is not found.
The lastIndexOf() method returns the index within the calling String object of the last occurrence of the specified value, searching backwards from fromIndex. Returns -1 if the value is not found.
The padEnd() method pads the current string with a given string (eventually repeated) so that the resulting string reaches a given length. The pad is applied from the end (right) of the current string.
The padStart() method pads the current string with a given string (eventually repeated) so that the resulting string reaches a given length. The pad is applied from the start (left) of the current string.
The static String.raw() method is a tag function of template literals, similar to the r prefix in Python or the @ prefix in C# for string literals (yet there is a difference: see explanations in this issue). It's used to get the raw string form of template strings (that is, the original, uninterpreted text).