template literal or string interpolation
uppercase and lowercase
slice()
the slice() method extracts a section of the string and returns it as a new string, without modifying the original string.
replace() and replaceAll()
The replace() method of String values returns a new string with one, some, or all matches of a pattern replaced by a replacement. The pattern can be a string or a RegExp, and the replacement can be a string or a function called for each match. If pattern is a string, only the first occurrence will be replaced. The original string is left unchanged.
The replaceAll() method of String values returns a new string with all matches of a pattern replaced by a replacement. The pattern can be a string or a RegExp, and the replacement can be a string or a function to be called for each match. The original string is left unchanged.
concat()
The concat() method of String values concatenates the string arguments to this string and returns a new string.
trim(), trimEnd() and trimStart()
The trim() method of String values removes whitespace from both ends of this string and returns a new string, without modifying the original string. To return a new string with whitespace trimmed from just one end, use trimStart() or trimEnd().
The trimEnd() method of String values removes whitespace from the end of this string and returns a new string, without modifying the original string. trimRight() is an alias of this method.
The trimStart() method of String values removes whitespace from the beginning of this string and returns a new string, without modifying the original string. trimLeft() is an alias of this method.
for...in loop
at()
The at() method of String values takes an integer value and returns a new String consisting of the single UTF-16 code unit located at the specified offset. This method allows for positive and negative integers. Negative integers count back from the last string character.
endsWith()
The endsWith() method of String values determines whether a string ends with the characters of this string, returning true or false as appropriate.
startsWith()
The startsWith() method of String values determines whether a string begins with the characters of a specified string, returning true or false as appropriate.
repeat()
The repeat() method of String values constructs and returns a new string which contains the specified number of copies of this string, concatenated together.
valueOf()
split()
The split() method of String values takes a pattern and divides this string into an ordered list of substrings by searching for the pattern, puts these substrings into an array, and returns the array.
includes()
The includes() method of String values performs a case-sensitive search to determine whether a given string may be found within this string, returning true or false as appropriate.