Detailed explanation of writing simple regular expressions

In the literal mode, all the contents wrapped between // are metacharacters, some have special meanings, and most of them are ordinary metacharacters that represent their own meaning

var name = 'wo';var reg = /^\d+"+name+"\d+$/

In order to solve the above-mentioned need to add a variable to the regular expression, we can only use the instance creation method

var reg = new RegExp("^\\d+"+name+"\\d+$","g")

Literal method and instance creation method are in regular expressions The difference?

#1. Everything that appears in the literal method is metacharacters, so variable values ​​cannot be spliced, but the instance creation method is possible.

2. Just write \d directly in the literal, but in the example it needs to be translated into \\d

Exercise rules:

1. Age between 18-65 // Age between 18-19 20-59 60-65

var reg = /^(1[8,9] | [2,5]\d | 6[0,5])$/

2. Verify the regularity of the email address ( Short version)

The rules on the left side of the mailbox: numbers, letters, underscores, ., -

var reg = /^[\w. -]+@[0-9a-zA-Z]+(\.[a-zA-Z]{2,4}){1,2}$/

##　3 , Chinese standard real name 2-4 Chinese characters

##　var reg = /^[\u4e00-\u9fa5]{2,4}$/

4. ID number

## var reg = /^\d{17}(\d | x)$/

var reg = /^\(d{2})(\d{4})(\d{4})(\d{2})(\d{2})(\d{2})(\d )(\d | X)$/

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