In my opinion, most of the front-end processing of data is the processing of strings and arrays, as well as objects. Because I can't remember these methods, I always confuse them, so I summarize them and write them down for easy reference and review.
First, the processing of strings,
1. contact --- Concatenate two or more strings together and return a string
string1.contact(string2)
2. indexOf --- returns the index (the index of one occurrence of a substring, starting from zero, or -1 if there is no match)
long string.indexOf(string)
3. charAt --- Returns the string at the specified position
long string.charAt(position)
4. lastIndexOf --- Returns the position of the last occurrence of the substring in the long string, if not, returns -1
long string.lastIndexOf(string)
5. match --- Query whether a string matches a regular expression, if not, return null
string.match(regular expression)
6. substring --- returns a string of long strings, passing in the start and end positions
substring (start bit, end bit)
7. substr --- returns a string, passing in the start bit and length
substr(start bit, length)