Getting started with regular expressions: match a Fixed Single Character

All single uppercase/lowercase letters, numbers, and special characters to be described later are a regular expression. They can only match a single character, and this character is the same as itself. For example, for the expression "I ":

welcome to visit www.bkjia.com

The following applet will match the lower-case letter I in the string welcome to visit www.bkjia.com, replace it with the upper-case letter I, and change the background color to orange.

Effect demonstration

Welcome to visit www.bkjia.com

Welcome to visit www.bkjia.com

Program code:

<script type="text/javascript">function reg_replace(){var str = "welcome to visit www.bkjia.com";var test = document.getElementById("test");regex = new RegExp("i","g");test.innerHTML = str.replace(regex,"<span style='background-color:orange'>I</span>");//alert(str.replace(regex,"I"));}function reg_split(){var str = "welcome to visit www.bkjia.com";var test = document.getElementById("split");regex = new RegExp("i","g");test.innerHTML = str.split(regex);//alert(str.replace(regex,"I"));}</script>

A combination of multiple fixed characters constitutes an expression that matches a fixed string. For example, "bkjia" is also a regular expression, which consists of multiple expressions that match a fixed character. It can only match any text exactly the same as it:

Effect demonstration

Welcome to visit www.bkjia.com

You can understand the matching process of the expression "bkjia" as follows: it consists of n, o, w, a, m, a, g, I, c is a fixed string of 9 characters. For each character, it can only match exactly the same character. When these 9 characters are combined, it matches the character string in the same order as the expression and at the same position as the corresponding character (in fact, it is a string exactly the same as the expression ).

Because this matching method is the least flexible, it can only match exactly the same characters, so it is also called "full match ".

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