How do you make a case sensitive?

Both String#includes() and String#indexOf() are case sensitive. Neither function supports regular expressions. To do case insensitive search, you can use regular expressions and the String#match() function , or you can convert both the string and substring to lower case using the String#toLowerCase() function.

indexOf() The indexOf() method, given one argument: a substring to search for, searches the entire calling string, and returns the index of the first occurrence of the specified substring .

Yes, it is case-sensitive. You can do a case-insensitive indexOf by converting your String and the String parameter both to upper-case before searching . Note that toUpperCase may not work in some circumstances.

JavaScript is a case-sensitive language . This means that language keywords, variables, function names, and any other identifiers must always be typed with a consistent capitalization of letters.

To convert all array elements to lowercase: