When you retrieve a text, you can use a pattern to describe what you want to retrieve. RegExp is this pattern.
A simple pattern can be a single character.
More complex patterns include more characters and can be used for parsing, format checking, substitution, and more.
You can specify where to search in a string, the type of character to search, and so on.
1. Basic usage
<script>
// Create regular var reg = /hello/
// Detect whether a string has text that conforms to regular format var flag = ("hello world")
(flag) // true
</script>
2. Modifier
Modifiers are used to perform case-sensitive and global matching
i is case insensitive
g Global Match
<script>
// By default, it will be case sensitive var reg = /hello/
var flag = ("Hello World")
(flag) // false
// Add i modifier case insensitive var reg2 = /hello/i
var flag2 = ("Hello World")
(flag2) // true
var str = "I'm in a bad mood, really bad"
// Default non-global matching var reg3 = /bad/
var newStr = (reg3,"good")
// Only one bad was replaced (newStr) // I'm in a good mood, really bad
// Global Match var reg4 = /bad/g
var newStr2 = (reg4,"good")
// Replace the global bad to good (newStr2) // I'm in a good mood, really good
// Use simultaneously var reg5 = /bad/gi
</script>
3. Metachar
Metacharacters are characters with special meanings:
. Find a single character, except for newlines and line endings. (In layman's terms, it's any character)
- \d Match numbers 0-9
- \D Match non-number
- \s Match any whitespace characters (no space limit)
- \S Match non-whitespace characters
- \w Metacharacter is used to find word characters. (Word characters include: a-z, A-Z, 0-9, and underscore)
- \W Metacharacter is used to find non-word characters.
4. Square brackets
Square brackets are used to find characters in a range
- [abc] Match a character in brackets (one of a, b, c)
- [^abc] Match a character that does not exist in brackets (characters other than a, b, and c)
- [0-9] Find any number from 0 to 9.
- [a-z] Find any character from lowercase a to lowercase z.
- [A-Z] Find any character from capital A to capital Z.
- [A-z] Find any character from uppercase A to lowercase z.
5. Quantitative words
- \d{6} Match 6 numbers
- \d{4,6} Match 4 to 6 numbers
- \d{4,} Match at least 4 numbers
- ? 0 or 1 More than 1 mismatch
- + At least 1
- * 0 or more
.* will match as long as possible characters (greed)
.*? Will match shorter characters as much as possible (greed is forbidden)
\d{4,6} will match as long as possible characters (greed)
\d{4,6}? Will match shorter characters as much as possible (greed is forbidden)
6. Boundary matching
^n matches any string that starts with n.
n$ matches any string with the ending n.
7. Example
Match mobile phone number
var reg = /^1\d{10}$/;
Match QQ number
var reg = /^[1-9]\d{4,10}$/;
Match ID number
var reg = /^[1-9]\d{16}[Xx\d]$/;
Variable name detection (can only consist of letters, numbers, and underscores, and cannot start with numbers, length 6-15)
var reg = /^[A-z_]\w{5,14}$/;
8. Related methods
test(): Detect whether a regular expression can find matching text in the specified string
<script>
var str = "hi66morning77"
// Match 3 consecutive numbers var reg = /\d{3}/
((str)) // false
// Match 7 consecutive lowercase letters var reg2 = /[a-z]{7}/
((str)) // true
</script>
match(): Find a string, return text that meets regular expression rules as an array, if no global match is specified, it is only searched once. Return null if not found
<script>
var str = "hi66morning77"
// Match 2 consecutive numbers Non-global match var reg = /\d{2}/
((reg)[0]) // 66
// Match 2 consecutive numbers Global match (recommended) var reg2 = /\d{2}/g
((reg2)) // ["66", "77"]
</script>
search(): Returns the index value of the target from the first occurrence of the string (so global matching is ignored)
<script>
var str = "hi66morning77"
// Match 2 consecutive numbers Non-global match var reg = /\d{2}/
((reg)) // 2
// Match one of a, b, m var reg2 = /[abm]/
((reg2)) // 4
</script>
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