Entry to regular expression: submode

In a regular expression, you can use "(" and ")" to enclose the sub-strings in the pattern to form a sub-pattern. When the sub-mode is regarded as a whole, it is equivalent to a single character.

Next we will try to match all the line breaks, including <br>, <br/>, and <br/>.

(<br\s*\/?>)

Effect demonstration

Welcome to bkjia.com.<br> Welcome to bkjia.com. *2<br><br/><br /> Welcome to bkjia.com. *3<br>>>>

This example code

function reg_replace(){var test = document.getElementById("test");var regex = /(<br\s*\/?>)/g;test.innerHTML = test.innerHTML.replace(regex,"<span style='background-color:orange'>$1</span>");}

We can understand the matching process as follows: Sub-mode "(<br \ s * \/?> )" First, match all "<br>", "<br/>", or "<br/>", and then treat each matching result as a whole (equivalent to a single character). Then, match the entire text that appears two or more times in a row.

Additional reading

The topic list of this article is as follows:

1. What is a regular expression?
2. Getting started with regular expressions: match a Fixed Single Character
3. Getting started with regular expressions: matching any single character
4. Getting started with regular expressions: Use character groups
5. Getting started with regular expressions: Use character ranges in character groups
6. Getting started with regular expressions: Use of assense character groups
7. Getting started with regular expressions: matching null characters
8. Getting started with regular expressions: Match one or more characters
9. Regular Expression: matches zero or multiple characters.
10. Regular Expression entry: matches zero or one string.
11. Getting started with regular expressions: Match fixed numbers of Characters
12. Getting started with regular expressions: match the number of characters in a range
13. Getting started with regular expressions: greedy matching
14. Getting started with regular expressions: inert matching
15. Entry to Regular Expressions: two matching Modes
16. Getting started with regular expressions: match word boundaries
17. Getting started with regular expressions: boundary definition and relativity
18. Getting started with regular expressions: Match non-word boundaries
19. Getting started with regular expressions: match the beginning and end of a text
20. Entry to regular expression: submode
21. Regular Expression entry: "or" Match
22. Getting started with regular expressions: replacing with referenced text
23. Getting started with regular expressions: unmatched
24. Regular Expression Summary: Regular Expressions in JavaScript
25. Regular Expression Summary: advanced application of regular expressions in js