string api

1. length - string.length
2. charAt - string.charAt(index)
3. charCodeAt - string.charCodeAt(index)
4. concat - string.concat(string1, string2, ..., stringX)
5. indexOf - string.indexOf(searchValue, fromIndex)
6. lastIndexOf - string.lastIndexOf(searchValue, fromIndex)
7. match - string.match(regexp)
8. replace - string.replace(searchValue, replaceValue)
9. search - string.search(regexp)
10. slice - string.slice(start, end)
11. substring - string.substring(start, end)
12. split - string.split(separator, limit)
13. includes - string.includes(searchValue, start)
14. startsWith - string.startsWith(searchString, position)
15. endsWith - string.endsWith(searchString, length)
16. toUpperCase - string.toUpperCase()
17. toLowerCase - string.toLowerCase()
18. trim - string.trim()
19. trimStart - string.trimStart()
20. trimEnd - string.trimEnd()
21. padStart - string.padStart(targetLength, padString)
22. padEnd - string.padEnd(targetLength, padString)
23. 模版字面量 - ${expression}
24. replace - string.replace(searchValue, replaceValue)
25. replaceAll - string.replaceAll(searchValue, replaceValue)