Getting started with regular expressions: Match fixed numbers of Characters

Although "?" The appearance of the three metacharacters "+" and "*" solves many problems. However, they are not perfect: 1. there is no way to specify the maximum number of matching characters. For example, if we want to match a mobile phone number, it should be 11 digits, while "+" and "*" will match as many numbers as possible, 17 or 18 are correct. 2. There is no way to specify the minimum number of matching characters, such as "+", "*", and "?". The minimum number of characters that can be provided is either zero or one.

In a regular expression, it can be in a single character (such as "j"), a character group (such as "[abcde]"), or a specific character type (such as "\ d "), any character (that is, ". ") followed by" {number} ", to match a string consisting of zero or multiple characters.

For example, "\ d {3}" can be used to match the number from 999 to 1000. When "a {6}" is used, it can match "aaaaaa" (or it can only match, because "a" is a fixed character ).

Now let's consider a more complex example. If we want to match the mobile phone number, the rule is: the first is "1", and the second is "3 or 5 ", any number with nine digits. Then its matching should be like this:

1[35][0-9]{9}

Effect demonstration

13536781234

18677530289

15345231123

This example code

function reg_replace(){var test = document.getElementById("test");aim = "1[35][0-9]{9}";var regex = new RegExp("("+aim+")","g");test.innerHTML = test.innerHTML.replace(regex,"<span style='background-color:orange'>$1</span>");}

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