how to use dotall flag for regex.exec()

Question

i want get to string in a multiline string that content any specific character and i want get to between two specific staring.

i used this regex and this work but if content have any character (\r \n \t) not work and get null value.

This Wotked
    var regex = new RegExp("\-{2}Head(.*)-{2}\/\Head");      
    var content = "--Head any Code and String --/Head";
    var match = regex.exec(content);

This Not Worked

var regex = new RegExp("\-{2}Head(.*)-{2}\/\Head");      
var content = "--Head \n any Code \n and String --/Head";
var match = regex.exec(content);

i found a regexer(http://www.regexr.com/v1/) and know i should use Dotall for multiline string but i cant use dotall for regex.exec

thanks.

Answer 1

In 2018, with the ECMA2018 standard implemented in some browsers for the time being, JS regex now supports s DOTALL modifier:

Browser support

console.log("foo\r\nbar".match(/.+/s)) // => "foo\r\nbar"

Actually, JS native match-all-characters regex construct is

[^]

It means match any character that is not nothing. Other regex flavors would produce a warning or an exception due to an incomplete character class (demo), though it will be totally valid for JavaScript (demo).

The truth is, the [^] is not portable, and thus is not recommendable unless you want your code to run on JS only.

regex = /--Head([^]*)--\/Head/

To have the same pattern matching any characters in JS and, say, Java, you need to use a workaround illustrated in the other answers: use a character class with two opposite shorthand character classes when portability is key: [\w\W], [\d\D], [\s\S] (most commonly used).

NOTE that [^] is shorter.

Answer 2

javascript doesn't support s (dotall) modifier. The only workaround is to use a "catch all" class, like [\s\S] instead of a dot:

regex = new RegExp("\-{2}Head([\\s\\S]*)-{2}\/\Head")

Also note that your expression can be written more concisely using a literal:

regex = /--Head([\s\S]*)--\/Head/