Character Set
JavaScript programs are written using the Unicode character set. Unicode is a superset of ASCII and Latin-1 and supports virtually every written language currently used on the planet. ECMAScript 3 requires JavaScript implementations to support Unicode version 2.1 or later, and ECMAScript 5 requires implementations to support Unicode 3 or later. See the sidebar in Text for more about Unicode and JavaScript.
Case Sensitivity
JavaScript is a case-sensitive language. This means that
language keywords, variables, function names, and other
identifiers must always be typed with a
consistent capitalization of letters. The while
keyword, for example, must be typed
“while,” not “While” or “WHILE.” Similarly, online
, Online
, OnLine
, and ONLINE
are four distinct variable
names.
Note, however, that HTML is not case-sensitive (although XHTML
is). Because of its close association with client-side JavaScript,
this difference can be confusing. Many client-side JavaScript
objects and properties have the same names as the HTML tags and
attributes they represent. While these tags and attribute names can
be typed in any case in HTML, in JavaScript they typically must be
all lowercase. For example, the HTML onclick
event handler attribute is
sometimes specified as onClick
in
HTML, but it must be specified as onclick
in JavaScript code (or in XHTML
documents).
Whitespace, Line Breaks, and Format Control Characters
JavaScript ignores spaces that appear between tokens in programs. For the most ...
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