This is my first article on getting started

preface

In daily work, regular expressions are more or less exposed to either front-end development or back-end development. Regular expressions can be used to solve the problems we encounter in development and improve our work efficiency

Three uses of front-end regular expressions

  1. Parse the URL to get the parameters in it
  2. Form validation
  3. Sensitive word filtering

Basic methods in regularization

1.test()

  • The result returned is a Boolean value
  • If true, it means that the string conforms to the rule
  • False indicates that the string does not conform to the rule
var reg = /a/
var str = "abc"
console.log(reg.test(str))
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2.exec()

  • Determines whether the target string contains characters that match the rule
  • Returns an array, if any, containing the proper characters, the subscript, and the target string
  • If not, return null
var reg = /a/
var str = "abc"
console.log(reg.exec(str))
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Character classes

  • [] is one digit. Empty [] indicates that any character can be matched
  • If there is a character in [], [ABC] means that a, B, or C in this position is consistent with the rule (note: matching lowercase letters can be written as [a-z])
  • The up arrow indicates no if written inside the character class, start if written outside the character class, and $indicates end
  • [A-Za-Z0-9] indicates that the digit is either a lowercase letter or a number

The basic characters of the

The title The title
[…]. Any character in square brackets
[^…]. Any other character except the square brackets
. Any character other than the newline and other Unicode terminators
\w Any ASCII character word equivalent to [a-za-Z0-0] and containing an underscore
\W Any word that does not consist of ASCII characters, equivalent to [^ a-za-z0-9_]
\s Any Unicode whitespace
\S Any character that is not Unicode whitespace, note the difference between \w and \s
\d Any ASCII number, equivalent to [0-9]
\D Any character other than an ASCII number, equivalent to [^0-9]

quantifiers

  • {m} is repeated m times
  • {n,m} means at least n and at most m occurrences
  • {n,} indicates the minimum number of occurrences
  • “+” is equivalent to {1,}
  • “*” is equivalent to {0,}
  • “?” Equivalent to {0, 1}

grouping

When () is used, it is equivalent to grouping the parentheses into a group. After grouping, the matching content can be retrieved from the group

The number following RegExp.&1 $indicates the number of groups

Parse the URL and obtain the name through the re

To fetch a group, you must run the re, e: reg.test(STR), before fetching.

If you want to write variables in a regular expression, declare the regular expression as an object

var reg = new RegExp(name+"= (/ ^ & *)")
reg.test(str)
// So we get the value after name. Name is the variable. This is the re that gets the value from the URL
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Filter text content

var reg = / brother/g
var str = "I'm the big brother and you're the big brother. Hello, brother."
str.replace(reg,"*")
/ / if you want to match brother and elder brother two word available candidates, namely reg = / brother / | Columbia, | said the candidate, and [brother elder brother]
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Note: g indicates global, I indicates case insensitive, and you can write it at the end

/\d{2,6}/ by default, the regular expression matches six digits. If you want to use lazy mode, add? That / \ d {2, 6}? /

See here smart you must have learned the re, congratulations!!