JavaScript regex to match the very precise number of the same characters-CodePudding

String example:

~~333~~

I need to get everything inbetween

~~

Regex that works:

/^(~{2})(.*?)(~{2})$/gm

But it also gets this string:

~~~333~~~

and also this:

~~~~333~~~~

What regex will get only the first one?

CodePudding user response：

The reason your regex is matching the latter two test cases is because of your wildcard character . is picking up the inner ~s. To fix this, and make it only match numbers you could do this:

/^~{2}([0-9]*)~{2}$/gm

If you want to catch other characters as well as long as they ae not ~ you could match all characters excluding the ~ character like this:

^~{2}([^~]*)~{2}$

Both of these only match the first test case ~~333~~ and not the others.

CodePudding user response：

You could use a lookaround approach on both ends to ensure that tilde does not precede or follow the ~~ markers.

var input = "~~333~~ ~~~444~~~ ~~~~5555~~~~";
var matches = input.match(/(?:^|[^~])~~([^~] )~~(?!~)/g);
console.log(matches);

CodePudding user response：

To get the string between the first set of double tildes (~~) and exclude strings with additional tildes, you can use the following regular expression:

/^(~{2})([^~]*)(~{2})$/gm

([^~]*): This matches zero or more characters that are not tildes ([^~]). The * specifies that the preceding character or group (in this case, the negated character class) should be matched zero or more times.

CodePudding user response：

The below regex will match for exact two '~' in beginning and at last. And any string between those.

/^(~{2})([^~]*)(~{2})$

CodePudding user response：

Try this:

^~~[^~\r\n] ~~$

^ match the start of the line.

~~ match two literal ~.

[^~\r\n] match one or more character that is not ~ because we don't want to cross the two closing ~~, and also not \r or \n because we also don't want to cross newline characters.

~~ match two literal ~.

$ match the end of the line.

See regex demo.