正则表达式需求：仅允许字母与连字符的输入匹配模式问题

Hey there! Here's a straightforward guide to applying Markdown formatting, with practical examples for each rule you mentioned:

Headings #

Use number signs (#) to define heading levels. More #s mean smaller headings (from level 1 to 6):

• # Main Heading → # Main Heading
• ## Subheading → ## Subheading
• ### Sub-subheading → ### Sub-subheading

Unordered List Items #

Start each list entry with a dash (-) to create an unordered list:

• First item in the list
• Second item, with a bit more detail
• Third item, maybe with a nested sub-item?
  • Yep, just indent the sub-item with spaces!

Emphasized Text #

Wrap text with asterisks (*) to make it italicized (emphasized):

• *This text stands out as emphasized* → This text stands out as emphasized

Inline Code & Commands #

Surround code snippets, commands, or technical terms with single backticks ( ) to format them as inline code:

• Run npm install to set up the project → Run npm install to set up the project

For multi-line code blocks, use three backticks (```) at the start and end (you can even add a language tag for syntax highlighting):

function calculateTotal(prices) {
  return prices.reduce((sum, price) => sum + price, 0);
}

Blockquotes #

Use greater than signs (>) to create quoted text blocks, perfect for citing sources or highlighting important notes:

This is a blockquote.
You can continue the quote across multiple lines by adding > at the start of each new line.

Links #

Format links by wrapping the display text in square brackets ([]), followed by the target URL in parentheses (()):

• [Check out this helpful guide](https://example.com/guide) → Check out this helpful guide

Images #

To add images, use square brackets ([]) for alt text (a description for screen readers), then the image URL in parentheses (()):

• [A scenic mountain view](https://example.com/mountain.jpg) → (This will render the image if the URL is valid; alt text shows if the image can't load)

内容的提问来源于stack exchange，提问作者Csabikaaaa