Javascript has a number of string manipulation operations which can be performed on it. So we have methods like concat(), slice(), match(), etc
My question is do all these string manipulation methods return a new string value as the result OR are there some methods which actually modify the actual string being used in the method ?
Strings in JavaScript (and many other languages) are implemented as immutable objects. This has a few beneficial properties:
This also means that all string methods must return a new string if they aim to modify the original value.
String.prototype.mutate = function (arg) { this = 'changed' } and JS interpreters will complain that you are supplying an invalid left-hand side in assignment.
String. this can't be set in any function as it's not a variable.The return value is a clone of the original string.
In other words, calling concat, match or slice will not modify the original string.
You can always refer to the MDN reference for documentation
But, to quote from the source
Concat
Combines the text of two or more strings and returns a new string.
Strings are immutable, and once they are created they even cannot be modified again.
Unlike in languages like C, JavaScript strings are immutable. This means that once a string is created, it is not possible to modify it. However, it is still possible to create another string based on an operation on the original string, for example, a substring of the original (by picking individual letters or using String.substr()) or a concatenation of two strings using the concatenation operator (+) or String.concat().
Therefore, yes. Every String operation returns a new String
