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1. Metacharacters:
Each regular expression is composed of metacharacters and modifiers
[Metacharacters] ->Some characters with special meaning between two /
reg = /^\d$/ //只能是一个0-9之间的数字
1. Characters with special meaning Metacharacter
## \: Escape character, translate the meaning of the following characters
^: Start with a certain metacharacter
$: ends with a metacharacter
\n: matches a newline character
.: Any character except \n
(): Grouping-> Divide a large regular pattern into several small regular patterns
x|y: One of x or y
[xyz]: One of x, y or z A
## [^xyz]: Any character except three[a-z]: Any character between a-z
[^a-z]: Except any character between a-z
\d: A character between 0-9 \D Any characters except numbers between 0-9
## \b: A boundary character "w1 w2 w3"
##\w: Any character among numbers, letters, and underscores [0-9a-zA-Z_]
##\s: Matches a whitespace character, a space, a tab character, a form feed character.. .
## 2. Quantifier metacharacter representing the number of occurrences*: Appear zero to multiple times
+ ： Appears 1 or more times
? ：Occurs zero or 1 times
{n} ：Occurs n times
{n,} :Occurs n to multiple times
{n,m}: appears n to m times
reg = /^\d+wo\d+$/; reg = /^(\d+)wo(\d+)$/;
var reg = /^0.2$/ // 以0开头 2结尾，中间可以是除了\n的任意字符
var reg = /^\d+$/;//只能是多个数字console.log(reg.test('2017'))//true//一个简单的验证手机号的正则:11位数字，第一位为1var reg = /^1\d{10}$/;
2. Application of metacharacters
[]1. All characters appearing in square brackets The characters are all characters that represent their own meaning (no special meaning).
2. Square brackets do not recognize two digits
var reg = /^[12-68]$/ -> ;Represents one of 1, 2-6, and one of 8. This method is wrong
()
1. Function 1 of grouping: Change the default priority of x|y
var reg = /^18|19$/;//符合条件的有18、19、181、189、119、819、1819
var reg = /^(18|19)$/ //18、191. Regular rules for valid numbers: positive numbers, negative numbers, zero, decimals
2), there may be +/- at the beginning or not
3), the integer part, A single digit can be one between 0-9, and multiple digits cannot start with 0
The regular rules are as follows
var reg = /^[+-]?(\d|([1-9]\d+))(\.\d+)?$/
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