正则表达式匹配具有准确标识符字符数的字符串

Question

Take the following paragraph:

#### And this will not work!
This is an *italic*... does it work!
This is a **bold** text and it will work!
Will this ***work***

I have built this regex /(?:\\*{2}.*?\\*{2})/gm to match words which start & end with ** characters. However, my regex also matches the last line Will this ***work*** , which I do not want it to.

How can I set a restriction to watch for the next character after the match not to be another * ?

Thank you.

Answer 1

I suggest using

string.match(/(?<!\*)\*{2}[^*]*\*{2}(?!\*)/g)

See the regex demo

Pattern details

• (?<!\\*) - a negative lookbehind that fails the match if there is an asterisk immediately to the left of the current location
• \\*{2} - double asterisk
• [^*]* - zero or more chars other than an asterisk
• \\*{2} - double asterisk
• (?!\\*) - a negative lookahead that fails the match if there is an asterisk immediately to the right of the current location

JavaScript demo:

 const string = "#### And this will not work!\\nThis is an *italic*... does it work!\\nThis is a **bold** text and it will work!\\nWill this ***work***"; console.log(string.match(/(?<!\\*)\\*{2}[^*]*\\*{2}(?!\\*)/g));

Answer 2

You can use [^\\*]* to match any number of characters that aren't an asterisk along with a negative look behind (?<!\\*) which checks that the preceeding character isn't an asterisk and negative look ahead (?!\\*) whcih checks that the following character isn't an asterisk:

 const str = `#### And this will not work! This is an *italic*... does it work! This is a **bold** text and it will work! Will this ***work***` console.log(str.match(/(?<!\\*)\\*{2}[^\\*]*\\*{2}(?!\\*)/g))