JavaScript: The Definitive Guide, Fourth Edition

Whitespace and Line Breaks

JavaScript ignores spaces, tabs, and newlines that appear between tokens in programs, except those that are part of string or regular expression literals. A token is a keyword, variable name, number, function name, or some other entity in which you would obviously not want to insert a space or a line break. If you place a space, tab, or newline within a token, you break it up into two tokens -- thus, 123 is a single numeric token, but 12 3 is two separate tokens (and constitutes a syntax error, incidentally).

Because you can use spaces, tabs, and newlines freely in your programs (except in strings, regular expressions, and tokens), you are free to format and indent your programs in a neat and consistent way that makes the code easy to read and understand. Note, however, that there is one minor restriction on the placement of line breaks; it is described in the following section.