什么是带有标题：[name]的正则表达式匹配？

Question

How to match the regex to the format "caption: [name]" ? I have used

^ ([a-zA-Z0-9]) + (. *?) + \: + (. *?) + $

but failed.

Answer 1

In your pattern you use spaces which have meaning. If you would remove all the spaces, your pattern would match and look like the following having 3 capturing groups:

^([a-zA-Z0-9])+(.*?)+\:+(.*?)+$

About the pattern

When you repeat the group using a quantifier (in this case + ), the group contains the value of the last iteration so you could move the quantifier inside the group.

The first group matches until caption . You could omit (.*?)+ as : is the next char and will be matched by \\:+ .

That part itself can be written as : because you don't have to escape the colon and you want to match a single : .

The second group is not taking the opening and closing square brackets into account. This could be matched using (\\[.*?\\]) or more efficient using a negated character class (\\[[^]]+\\])

If you want to keep the capturing groups, you pattern might look like:

^([a-zA-Z0-9]+): (\[[^\]]+\])$

Regex demo

Answer 2

In your current regex you have lots of problems

• ^ - This means match space after start of string whereas your input string doesn't have any
• ([a-zA-Z0-9])+ - This means match group one or more time, ie this tries to match repetitive characters
• (. *?) - This means match any one character followed by zero or more space characters
• + - This means one or more space characters

You can use

/^[a-zA-Z0-9]+\s*:\s*\[[^\]]+\]$/

 let str = "caption: [name]" let reg = /^[a-zA-Z0-9]+\\s*:\\s*\\[[^\\]]+\\]$/ console.log(reg.test(str)) 

Answer 3

I'm guessing that you wish to design an expression similar to:

^([^:]+)\s*:\s*(\[[^\]]+\])$

and capture caption and [name] .

---

The expression is explained on the top right panel of this demo if you wish to explore/simplify/modify it.

 const regex = /^([^:]+)\\s*:\\s*(\\[[^\\]]+\\])$/gm; const str = `caption: [name] other_captions: [other_names]`; let m; while ((m = regex.exec(str)) !== null) { // This is necessary to avoid infinite loops with zero-width matches if (m.index === regex.lastIndex) { regex.lastIndex++; } // The result can be accessed through the `m`-variable. m.forEach((match, groupIndex) => { console.log(`Found match, group ${groupIndex}: ${match}`); }); }