According to B station teacher Ono Mori regular expression course organized notes
Course links
escape
Escape symbols and escape characters
Special escape characters
\ n line
Enter \ r
\ T TAB -> TAB key 4 Spaces
String newline
Method three: You can define multi-line strings with backquotes
Regular expression
RegExp = regular expression
Early experience
Instantiation mode
Object direct quantity
If variables are to be used, they must be instantiated
Pay attention to
The modifier gim
The expression []
[]
What is each of the three consecutive characters
Range of writing
^ symbol
| or
metacharacters
Metacharacters are escape characters used by the re
\w \W
\d \D
\s \S
Matches a whitespace character
\b \B
.
Can match all characters except carriage return \r and newline \n
quantifiers
Rules of regular matching:
From left to right, the string matches more and then less. If the string matches once, it does not match back.
Greedy matching principle: can match many, never match few
n+
{1, plus infinity}
n*
{0, plus infinity}
An asterisk is a string that matches zero or more occurrences of any character in the range n,
If you match it multiple times first, after you match it multiple times, the null character counts as zero, so that’s fine.
n?
{0, 1}
n{x,y}
Do not scribble Spaces in regular expressions
Y does not write the default {1, infinity} === n+
X =0,y does not write default {0, infinity} === n*
^n
Matches any string beginning with n, this example is wrong, should be [‘ab’, ‘ab’]
n$
Matches any string ending in n,
The problem
Check whether the string starts and ends with abcd
Check whether the string starts or ends with abcd
Check whether the string starts and ends with abcd and has a number in the middle
Reg = / ^ abcd [\ d] + abcd $/ can
Matches an 11-digit cell phone number starting with 138
a(? =n)
A forward lookup matches string A immediately after the specified string n
a(? ! n)
The match is followed by string A that does not specify string n, also known as forward lookup
xxxx xxyy
subexpression
(a) in parentheses are subexpressions
Subexpressions are memorized, and subsequent backreferences are considered to match the same character
backreferences
\1 means that you backreference the first subexpression
\n means that you backreference the NTH subexpression
xxyy
(? :n)
Str.match catches the subexpression as well
Capture the packet
All three subexpressions a, b, and c are captured
No capture grouping
(? :a) disallow the capture of this subexpression
Regular object properties
Regular object method
reg.test(str)
reg.exec()
This method is a mechanical loop
features
Need to know the phenomenon
The index property in the output array is the same as the reg.lastIndex property, and can be changed by changing the reg.lastIndex value, that is, changing the matching position
But if you change lastIndex to something other than a multiple of 3, the next index will be the smallest multiple of 3 greater than lastIndex:
When reg. Exec (STR) is executed, lastIndex automatically synchronizes with index to 9
str.match(reg)
Mobile phone number check
Date of birth check
The difference between Match and Exec
str.split(reg)
String splitting
The method of the object constructed by String
str.toUpperCase()
str.toLowerCase()
str.toLocaleUpperCase()
str.toLocaleLowerCase()
For some special languages, such as Turkish, which have special letters and case, the locale is used to convert the case of these languages
The case conversion function can be implemented for English letters with or without locale
str.charAt()
str.charCodeAt()
str.fromCharCode()
str.substr()
Length after front closure
str.substring()
Before closed after opening
ValueOf and toString comparison
1. ToString String valueOf returns the original value
2, Date: toString indicates the time unique string value0f 13-bit millisecond timestamp
3, array: toString array elements used, split the string value0f array original value
Object: The type of the toString object. The string represents the original value of the object ‘[Object object]’ value0f
5. ToString function distinguishes between built-in JS functions and custom functions through [native code]
6, toString receives a parameter – radix Value0f has no parameter
Encapsulate utility class functions
The first kind of
The second,
Greedy mode and non-greedy mode
Greed mode by default, plus one? Go into non-greedy mode
Example 1
Example 2
replace
He doesn’t have the global matching capability
First argument: the string to replace
The second argument: the string to replace
xxyy -> yyxx
Method one:
Method 2:
js-plus-plus -> jsPlusPlus
Parentheses must be used for subexpression
jsPlusPlus -> js_plus_plus
aabbcc -> a
c$
If you use the $sign, you should write two: $$
You could view it as 1 $$2 $3
Zero or more occurrences
1000000000000 – > 1000000000000
Tip: Replace empty Spaces with commas
Matches that are followed by 1 or more 000 and the string ends with their null, change this null to a comma
The template to replace
Double brace substitution
Always remember to write subexpressions
Template replacement (critical)
Input fields do not allow input Spaces
At least 6
Validation email
Pay attention to the point
Any symbols in the syntax must be escaped, otherwise a syntax error will be reported
