In JavaScript, you can convert strings to different case formats using built-in methods. Here are the common case conversion methods: toLowerCase(): Converts a string to lowercase. toUpperCase(): Converts a string to uppercase. charAt(): Returns the character at a specified index within a string. substring(): Returns a new string containing a specified portion of the original string. slice(): Extracts a section of a string and returns it as a new string. replace(): Searches a string for a specified value or a regular expression, and returns a new string where the specified values are replaced. split(): Splits a string into an array of substrings based on a specified separator. Here's an example demonstrating these methods for case conversion: let str = "Hello, World!"; console.log(str.toLowerCase()); // Output: hello, world! console.log(str.toUpperCase()); // Output: HELLO, WORLD!