JavaScript 2.0-The Complete Reference, Second ... - freecodingtutorial

would match ―abcx7d‖ or ―abc_-d.‖ Other common classes are \s, any whitespace character; \S,
any non-whitespace character; \w, any word character; \W, any non-word character; \d, any
digit; and \D, any non-digit. (Notice the pattern: the uppercase version of shorthand is the
opposite of the lowercase). The complete list of character classes is given in Table 8-4.
Table 8-4: Regular Expression Character Classes
Character Meaning
>[chars] Any one character indicated either explicitly or as a range between the
brackets.
>[^chars] Any one character not between the brackets represented explicitly or as
a range.
>. Any character except newline.
>\w Any word character. Same as [a-zA-Z0-9_].
>\W Any non-word character. Same as [^a-zA-Z0-9_].
>\s Any whitespace character. Same as [ \t\n\r\f\v].
>\S Any non-whitespace character. Same as [^ \t\n\r\f\v].
>\d Any digit. Same as [0-9].
>\D Any non-digit. Same as [^0-9].
>\b A word boundary. The empty ―space‖ between a \w and \W.
>\B A word non-boundary. The empty ―space‖ between word characters.
>[\b] A backspace character.
We can use these shorthands to write an even more concise version of our isPhoneNumber()
function:
function isPhoneNumber(phone) { var pattern = /^\d{3}-\d{3}-\d{4}$/; return pattern.test(phone);}
We‘ve replaced each [0-9] character class with its shorthand, \d.
Alternatives
The final major tool necessary to define useful patterns is |, which indicates the logical OR of
several items. For example, to match a string that begins with ―ftp,‖ ―http,‖ or ―https,‖ you might
write
var pattern = /^(http|ftp|https)/;
Unlike repetition quantifiers that only apply to the previous item, alternation separates complete
patterns. If we had written the preceding example as
var pattern = /^http|ftp|https/;
the pattern would have matched a string beginning with ―http‖ or a string containing ―ftp‖ or a
string containing ―https.‖ The initial ^ would‘ve been included only in the first alternative pattern.
To further illustrate, consider the following regexp:
var pattern = /James|Jim|Charlie Brown/;
Since each | indicates a new pattern, this matches a string containing ―James,‖ a string
containing ―Jim,‖ or a string containing ―Charlie Brown.‖ It does not match a string containing
―James Brown‖ as you might have thought. Parenthesizing alternatives limits the effect of the |
to the parenthesized items, so you see the following pattern,