Variable Names

It must be a legal identifier. An identifier is an unlimited series of Unicode characters that begins with a letter.
It must not be a keyword , a boolean literal (true or false), or the reserved word null.
It must be unique within its scope. A variable may have the same name as a variable whose declaration appears in a different scope. In some situations, a variable may share the same name as another variable if it is declared within a nested block of code.

It must be a legal identifier. An identifier is an unlimited series of Unicode characters that begins with a letter.