// /pattern/flags
let re1 = /abc/i;
re1.test( 'aBcd' ); // true
// new RegExp( pattern[, flags] )
let re2 = new RegExp( 'a', 'g' );
'aaa'.match( re2 ); // ["a", "a", "a"]| Flag | Description |
|---|---|
| g | global match |
| i | ignore case |
| m | multiline: treat beginning (^) and end ($) characters as working over multiple lines |
| u | unicode: treat pattern as a sequence of unicode code points |
| y | sticky: matches only from the index indicated by the lastIndex property of this regular expression in the target string (and does not attempt to match from any later indexes) |
| Character | Meaning |
|---|---|
| . | any single character except line terminators: [^\n\r\u2028\u2029] |
| \d | [0-9] |
| \D | [^0-9] |
| \w | [A-Za-z0-9_] |
| \W | [^A-Za-z0-9_] |
| \s | [ \f\n\r\t\v\u00a0\u1680\u180e\u2000-\u200a\u2028\u2029\u202f\u205f\u3000\ufeff] |
| \S | [^ \f\n\r\t\v\u00a0\u1680\u180e\u2000-\u200a\u2028\u2029\u202f\u205f\u3000\ufeff] |
| [\b] | backspace |
| \cX | control character in a string, where X is a letter from A-Z. For example, /\cM/ matches control-M in a string |
| \ | toggle next character treating between special/literal |
| [^] | any character that is not in the empty set of characters (including newlines) |
/[abcd]/ is identical to /[a-d]/ // but not equal ('===') due it's an object
/[^abc]/ is identical to /[^a-c]/ // matches negated or complemented character set// x|y
/a|b/.exec( 'ac' ); // ["a"]
/a|b/.exec( 'bc' ); // ["b"]| Character | Meaning |
|---|---|
| ^ | beginning of input. If the multiline flag is set to true, also matches immediately after a line break character |
| $ | end of input. If the multiline flag is set to true, also matches immediately before a line break character |
| \b | word boundary: position where a word character is not followed or preceeded by another word-character, such as between a letter and a space. Matched word boundary is not included in the match. |
| \B | non-word boundary: position where the previous and next character are of the same type: Either both must be words, or both must be non-words. Such as between two letters or between two spaces. |
RegExp.length; // 2Returns the RegExp constructor.
// RegExp[Symbol.species]
RegExp[Symbol.species]; // function RegExp() { [native code] }Read/write integer property of RegExp instances for the index at which to start the next match. Sets and updates automatically if the RegExp instance use the 'g' flag.
// regExpObj.lastIndex
let re = /a/g;
re.exec( 'aba' ); // ["a"]
re.lastIndex; // 1
re.exec( 'aba' ); // ["a"]
re.lastIndex; // 3
re.exec( 'aba' ); // null
re.lastIndex; // 0Works because of automatic updates of lastIndex property.
let str = 'a1b2c33';
let re = /\d+/g;
let match;
while ( match = re.exec(str) ) {
console.log( match[0], "at", match.index ); // 1 at 1; 2 at 3; 33 at 5
}Returns a string consisting of the flags of the current RegExp.
/ /ig.flags; // "gi"
/ /myu.flags; // "muy"Indicates whether or not the "g" flag is used with the RegExp.
/foo/g.global; // true
/bar/.global; // falseIndicates whether or not the "i" flag is used with the RegExp.
/foo/i.ignoreCase; // true
/bar/.ignoreCase; // falseIndicates whether or not the "i" flag is used with the RegExp.
/foo/m.multiline; // true
/bar/.multiline; // falseReturns a String containing the source text of the regexp, and it doesn't contain the two forward slashes on both sides and any flags.
/foo/gmu.source; // "foo"
// starting from ECMAScript 5
new RegExp().source; // "(?:)"
new RegExp( '\n' ).source === "\n"; // prior to ES5
new RegExp( '\n' ).source === "\\n"; // starting with ES5Indicates whether or not the "y" flag is used with the RegExp.
/foo/y.sticky; // true
/bar/.sticky; // falseIndicates whether or not the "u" flag is used with the RegExp.
/\u{61}/u.unicode; // true
/bar/.unicode; // false