They don’t have to wait for a page reload to see if they have forgotten to enter something. You can create interfaces that react when the user hovers over them with a mouse or activates them via the keyboard. This has been kept for security reason. This means that language keywords, variables, function names, and any other identifiers must always be typed with a consistent capitalization of letters.
An array has a length property that is useful for iteration. How to define a named function? A named function has a name when it is defined. How to define a anonymous function? An anonymous function can be defined in similar way as a normal function but it would not have any name.