Getting started with regular expressions: match word boundaries

Let's take a simple example.

The regular expression is as follows:

magic

Effect demo welcome to bkjia this magic place!

This example code

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

Obviously, we usually only want to match magic, instead of the magic that appears in bkjia.

In a regular expression, you can add "\ B" before the character to match the character following it at the first place of the string.

The character mentioned later refers to a single character (such as "j"), a character group (such as "[abcde]"), and a specific character type (such as "\ d "), escape special character "\ [" or a single arbitrary character (that is, ". ").

Let's take a look at this example:

Effect demo welcome to bkjia this magic place!

This time, the matching is correct. With the example of a single character just now, this expression is well understood: "\ B" only specifies that the character "m" must appear in the first place of the string, next, the characters a, g, I, and c are required. The matching of these two characters is irrelevant to "\ bm". They belong to the category of fixed character matching.

In a regular expression, you can add "\ B" after the character to match the character at the end of the string.

\ Bmagic \ B. This regular expression must start with m and end with c.

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