The lexer recognizes several nonreserved words that have special meanings in some contexts but can be used as identifiers. Numerals may be followed by units. Semicolon insertion on line breaks are both disabled in strict mode . Comments and White Space Comments and white space behave just like in JavaScript 1.5. Before the end of the program Semicolons are optional in these situations even if they would construct empty statements.
Strict mode has no effect on semicolon insertion in the above cases.
In addition, sometimes line breaks in the input stream are turned into VirtualSemicolon tokens. This kind of VirtualSemicolon insertion does not occur in strict mode . See also the semicolon insertion syntax rationale . This unfortunate dependence of lexical parsing on grammatical parsing is inherited from JavaScript 1.5. See the regular expression syntax rationale for a discussion of the issues.