请求用于检测字符串中项目编号（含标题与子标题）的正则表达式

Hey there! Let's build the regex you need to detect those list item numbers (including both top-level and subheadings) based on your examples.

First, let's break down the patterns we need to cover:

• Numeric numbers with or without a trailing dot (like 1. or 1)
• Asterisk bullet points (*)
• Multi-level numeric numbers (like 1.1 or 2.1)

Here's a flexible regex that can match all these cases, accounting for possible leading whitespace (since lists are often indented):

^\s*(?:(\d+(?:\.\d+)*\.?|\*)\s+)

Let me break down what each part does:

• ^\s*: Matches any leading whitespace at the start of a line (handles indented lists)
• (?:...): A non-capturing group to group our different numbering patterns together
  • \d+(?:\.\d+)*\.?: This covers numeric numbers:
    • \d+: Matches one or more digits (the main number)
    • (?:\.\d+)*: Optional repeated groups of a dot followed by digits (handles multi-level like 1.1, 1.1.2, etc.)
    • \.?: Makes the trailing dot optional (so it matches both 1 and 1.)
  • |: The "or" operator to include the asterisk pattern
  • \*: Matches the asterisk bullet point
• \s+: Matches one or more whitespace characters after the number/bullet (separating it from the content)

If you want to capture the actual number/bullet itself (instead of just detecting it), you can convert the non-capturing group to a capturing group by removing the ?::

^\s*((\d+(?:\.\d+)*\.?|\*)\s+)

Let's test this against your examples:

1. For 1. Hello 2. World: It will match 1. and 2.
2. For 1 Hello 2 World: It will match 1 and 2
3. For * Hello * World: It will match * and *
4. For 1 Hello1 1.1 Word1 2 Hello2 2.1 World2: It will match 1 , 1.1 , 2 , and 2.1

One quick note: This regex assumes the list items start at the beginning of a line (or with indentation). If you need to match numbers anywhere in a string (not just line starts), you can remove the ^ anchor.

内容的提问来源于stack exchange，提问作者Ibrar Ahmed