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4.1 .

`\`	: , . , `/b/` 'b'. b, . `/\b/`, , . , . , `` , 0 ; , `/a/` 0 . , ; , `/a\/` 'a*'. \ new RegExp("pattern") \ .
`^`	. , . , `/^A/` 'A' "an A", 'A' "An E". . , `/[^a-z\s]/` 'I' "I have 3 sisters".
`$`	. , . , `/t$/` 't' "eater", "eat".
`*`	0 . {0,}. , `/bo*/` 'boooo' "A ghost booooed" 'b' "A bird warbled", "A goat grunted".
`+`	1 . {1,}. , `/a+/` 'a' "candy" 'a' "caaaaaaandy".
`?`	0 1 . {0,1}. , `/e?le?/` 'el' "angel" 'le' "angle" 'l' "oslo". `*`, `+`, `?`, `{}`, "" ( ), , "" ( ). , /\d+/ "123abc" "123", /\d+?/, "1" . (assertions), x(?=y) x(?!y) .
`.`	( ) . , `/.n/` 'an' 'on' "nay, an apple is on the tree", 'nay'.
`(x)`	'x' . . , `/(foo)/` 'foo' "foo bar." `[1]`, ..., `[n]`.
`(?:x)`	'x' . - . `[1]`, ..., `[n]`.
`x(?=y)`	'x' 'x' 'y'. . , `/Jack(?=Sprat)/` 'Jack' 'Sprat'. `/Jack(?=Sprat\|Frost)/` 'Jack' 'Sprat' 'Frost'. , 'Sprat' 'Frost' .
`x(?!y)`	'x' 'x' 'y'. . , `/\d+(?!\.)/` . `/\d+(?!\.)/.exec("3.141")` '141' '3.141'.
`x\|y`	'x' 'y'. , `/green\|red/` 'green' "green apple" 'red' "red apple."
`{n}`	n - . `n` . , `/a{2}/` 'a' "candy," "caandy," "caaandy."
`{n,m}`	m n - . `n` `m` . m=n=1 . , `/a{1,3}/` "cndy", 'a' "candy," "caandy," "caaaaaaandy". , "caaaaaaandy", "aaa", .
`[xyz]`	. . , . ( (`.`) (`*`)) . . . , `[abcd]` [`a-d]`. 'b' "brisket" 'c' "city". `/[a-z.]+/` `/[\w.]+/` "test.i.ng".
`[^xyz]`	. , . . , , . , `[^abc]` `[^a-c]`. 'r' "brisket" 'h' "chop."
`[\b]`	(U+0008). ( `\b`.)
`\b`	. , . , . , . ( `[\b]`.) : `/\bmoo/` 'moo' "moon" ; `/oo\b/` 'oo' "moon", 'oo' 'n' , ; `/oon\b/` 'oon' "moon", 'oon' , , ; `/\w\b\w/` , , . Note: JavaScript's regular expression engine defines a specific set of charactersto be "word" characters. Any character not in that set is considered a word break. This set of characters is fairly limited: it consists solely of the Roman alphabet in both upper- and lower-case, decimal digits, and the underscore character. Accented characters, such as "" or "" are, unfortunately, treated as word breaks.
`\B`	. , : , . . , `/\B../` 'oo' "noonday" (, `/y\B./` 'ye' "possibly yesterday."
`\cX`	X . . , `/\cM/` control-M (U+000D) .
`\d`	. `[0-9]`. , `/\d/` or `/[0-9]/` '2' "B2 is the suite number."
`\D`	. `[^0-9]`. , `/\D/` or `/[^0-9]/` 'B' "B2 is the suite number."
`\f`	(U+000C). .
`\n`	(U+000A).
`\r`	(U+000D).
`\s`	, , , , . `[ \f\n\r\t\v\u00A0\u1680\u180e\u2000\u2001\u2002\u2003\u2004\u2005\u2006\u2007\u2008\u2009\u200a\u2028\u2029\u2028\u2029\u202f\u205f\u3000]`. , `/\s\w*/` ' bar' "foo bar."
`\S`	. `[^ \f\n\r\t\v\u00A0\u1680\u180e\u2000-\u200a\u2028\u2029\u202f\u205f\u3000]`. , `/\S\w*/` 'foo' "foo bar."
`\t`	(U+0009).
`\v`	(U+000B).
`\w`	. `[A-Za-z0-9_]`. , `/\w/` 'a' "apple," '5' "$5.28," '3' "3D."
`\W`	. `[^A-Za-z0-9_]`. , `/\W/` or `/[^A-Za-z0-9_]/` '%' "50%."
`\n`	n , , n , ( ). , `/apple(,)\sorange\1/` 'apple, orange,' "apple, orange, cherry, peach."
`\0`	NULL (U+0000). , `\0<digits>` .
`\xhh`	hh ( )
`\uhhhh`	hhhh ( ).

, , :

function escapeRegExp(string) {
  return string.replace(/[.*+?^${}()|[\]\\]/g, "\\$&"); // $& means the whole matched string
}

. , Using Parenthesized Substring Matches.

, /Chapter (\d+)\.\d*/ , . 'Chapter ', (\d , '+' 1 ), ( ; ' \' , '.'), 0 ('\d' , '*' 0 ). , .

"Open Chapter 4.3, paragraph 6" '4' . "Chapter 3 and 4", '3'.

, , ' ?:'. , (?:\d+) , .

test exec RegExp match, replace, search, split String. JavaScript


`exec`	`RegExp,` . .
`test`	`RegExp`, . .
`match`	`String`, . null .
`search`	`String,` . , -1 .
`replace`	`String`, , , .
`split`	`String,` .

, test search; exec match ( ). exec match , RegExp . , exec null ( false).

. , exec .

var myRe = /d(b+)d/g;
var myArray = myRe.exec("cdbbdbsbz");

, myArray :

var myArray = /d(b+)d/g.exec("cdbbdbsbz");

, :

var myRe = new RegExp("d(b+)d", "g");
var myArray = myRe.exec("cdbbdbsbz");

, . .

Table 4.3
			.
`myArray`		.	`["dbbd", "bb"]`
	`index`	( ).	`1`
	`input`	.	`"cdbbdbsbz"`
	`[0]`	.	`"dbbd"`
`myRe`	`lastIndex`	. . ( g, [Advanced Searching With Flags](#Advanced_Searching_With_Flags).)	`5`
`myRe`	`source`	. , .	`"d(b+)d"`

, , , . , , . , :

var myRe = /d(b+)d/g;
var myArray = myRe.exec("cdbbdbsbz");
console.log("The value of lastIndex is " + myRe.lastIndex);

The value of lastIndex is 5

, :

var myArray = /d(b+)d/g.exec("cdbbdbsbz");
console.log("The value of lastIndex is " + /d(b+)d/g.lastIndex);

The value of lastIndex is 0

/d(b+)d/g , , lastIndex. , , .

"" . , /a(b)c/ 'abc' 'b'. Array elements [1], ..., [n].

. , . .

replace(), () . $1 $2 .

var re = /(\w+)\s(\w+)/;
var str = "John Smith";
var newstr = str.replace(re, "$2, $1");
console.log(newstr);

"Smith, John".

, . , .

Flag	Description
`g`	.
i	.
m	.
y	, lastindex .

var re = /pattern/flags;

var re = new RegExp("pattern", "flags");

, . .

, re = /\w+\s/g , , .

var re = /\w+\s/g;
var str = "fee fi fo fum";
var myArray = str.match(re);
console.log(myArray);

["fee ", "fi ", "fo "]. :

var re = /\w+\s/g;

var re = new RegExp("\\w+\\s", "g");

m , . m , ^ $ .

. .

. string.split() string.replace(). , ( ) , . , ( ) .

// The name string contains multiple spaces and tabs,
// and may have multiple spaces between first and last names.
var names = "Harry Trump ;Fred Barney; Helen Rigby ; Bill Abel ; Chris Hand ";

var output = ["---------- Original String\n", names + "\n"];

// Prepare two regular expression patterns and array storage.
// Split the string into array elements.

// pattern: possible white space then semicolon then possible white space
var pattern = /\s*;\s*/;

// Break the string into pieces separated by the pattern above and
// store the pieces in an array called nameList
var nameList = names.split(pattern);

// new pattern: one or more characters then spaces then characters.
// Use parentheses to "memorize" portions of the pattern.
// The memorized portions are referred to later.
pattern = /(\w+)\s+(\w+)/;

// New array for holding names being processed.
var bySurnameList = [];

// Display the name array and populate the new array
// with comma-separated names, last first.
//
// The replace method removes anything matching the pattern
// and replaces it with the memorized stringsecond memorized portion
// followed by comma space followed by first memorized portion.
//
// The variables $1 and $2 refer to the portions
// memorized while matching the pattern.

output.push("---------- After Split by Regular Expression");

var i, len;
for (i = 0, len = nameList.length; i < len; i++) {
  output.push(nameList[i]);
  bySurnameList[i] = nameList[i].replace(pattern, "$2, $1");
}

// Display the new array.
output.push("---------- Names Reversed");
for (i = 0, len = bySurnameList.length; i < len; i++) {
  output.push(bySurnameList[i]);
}

// Sort by last name, then display the sorted array.
bySurnameList.sort();
output.push("---------- Sorted");
for (i = 0, len = bySurnameList.length; i < len; i++) {
  output.push(bySurnameList[i]);
}

output.push("---------- End");

console.log(output.join("\n"));

. , . "Check", . ( ), . , , .

(?:, \d{3} | $, \d{3}, $, ( )), , , , , ([-\/\.]), \d{3}, , \1, \d{4}.

0 $?, \d{3}, 0 $?, , , ([-\/\.]), . \d{3}, followed by the remembered match of a dash, forward slash, or decimal point \1, followed by four digits \d{4}.

"" , , "Enter".

html

<!doctype html>
<html>
  <head>
    <meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1" />
    <meta http-equiv="Content-Script-Type" content="text/javascript" />
    <script type="text/javascript">
      var re = /\(?\d{3}\)?([-\/\.])\d{3}\1\d{4}/;
      function testInfo(phoneInput) {
        var OK = re.exec(phoneInput.value);
        if (!OK)
          window.alert(RegExp.input + " isn't a phone number with area code!");
        else window.alert("Thanks, your phone number is " + OK[0]);
      }
    </script>
  </head>
  <body>
    <p>
      Enter your phone number (with area code) and then click "Check". <br />The
      expected format is like ###-###-####.
    </p>
    <form action="#">
      <input id="phone" /><button
        >
        Check
      </button>
    </form>
  </body>
</html>

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