Thanks for checking out my new article: Regular Expressions for JavaScript Hacks You Should Know

Regular expressions are logical, flexible, and functional. ② It can quickly achieve complex control of strings in a minimalist manner.

Use of regular expressions

Concept: regular expressions in JS are the creation and use of regular expressions stored as objects


//1 Creates a regular expression
let rg = / 123 /
// Expression validation

console.log(rg.test('123'));  
Call test() and pass in the string or number you want to validate. Test returns true or false
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The border characters ^ and $

So the first thing we have to figure out is what does this notation mean?^This is the starting position $That’s where it ends. Ok, so let’s look at the code.


let rg = /^acb$/   // AcB must start with A and end with B

console.log(rg.test('acb'));  //true
console.log(rg.test('bca'));  //false
console.log(rg.test('cab'));  //false
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The character class []

Represents a series of character choices that match only one of them

if[]There is a^Notice the opposite meaning.

// Let's look at the following code
let rg = /[acb]/  // Return true whenever a or b or c is included

console.log(rg.test('abc'));  //true
console.log(rg.test('bca'));  //true
console.log(rg.test('test'));  //false
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Scope operator [-]

Represents a restriction on the type obtained

let rg = /^[a-z]$/  // Return true for all 26 letters

console.log(rg.test('abc'));  //true
console.log(rg.test('bca'));  //true
console.log(rg.test('test'));  //true
console.log(rg.test(1));  //false
console.log(rg.test('A'));  //false // Case sensitive.
// If you want to add multiple validation rules, just look at the previous character spelling. For example, IF I want to verify that the username supports case and number, I can write like this.
let rg = /^[a-zA-Z0-9]$/  // Be careful not to add Spaces between them.
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Quantifier {}

The number of occurrences of a certain pattern. The validation rule we just wrote can only judge a single character, which is not practical in real development, so we need to limit the number of occurrences of a character.

  }

  let rg = / ^ [a zA - Z0-9] {6, 8} $/  // No Spaces! Indicates that the character being validated has at least six and up to eight bits

console.log(rg.test('test'));  //false
console.log(rg.test('test11'));  //false
console.log(rg.test('123456789'));  //false


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