Hey, firstly, great article! However, in your regex replace example, I believe something's missing? Running the following will throw an error: Uncaught ReferenceError: str is not defined var heyStr = "Hey now!" ; var byeStr = "Bye" ; var res = str.replace( "Hey" , "Bye" ) //returns ; Shouldn't res = heyStr.replace("Hey", "Bye") ? Similarly, the str.search() example is missing. Let me know if I'm missing something?