preface

String manipulation: array manipulation: array manipulation: array manipulation: array manipulation: array manipulation: array manipulation: array manipulation: array manipulation: array manipulation: array manipulation

String definition

Strings are wrapped in single or double quotation marks in js

const str = 'hello'
const username = "Leo"
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Two, common methods

1. str.length

You can get the following code for the length of the string (example) :

let username = 'leo'

console.log(username.length) / / 3
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2. charAt()

If you pass in an index value, you get the following character code for the index value (example) :

let str = 'Hi~ Leo'

console.log(str.charAt(4)) // L
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Note: space also counts as a character

3. concat()

The code for concatenating two strings is as follows (example) :

let str = 'Hi~'
let username = 'Leo'

console.log(str.concat(username)) // Hi~Leo
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4. includes()

Used to check if a string contains a string, returns a Boolean as shown in the following example:

const str = 'Hello Leo'

console.log(str.includes('Leo')) // true
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5. match()

This method returns an array after passing the regular check. The code that fails to return null looks like this (example) :

let username = 'Leo'
let userName = 'leo1'
// Matches a re that begins with a lowercase letter
const reg = /^[a-zA-Z]+$/

console.log(username.match(reg)) // ["Leo", index: 0, input: "Leo", groups: undefined]
console.log(userName.match(reg)) // null
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6. replace()

You can change the first qualified character in the string to the specified character code as follows (example) :

let tel = '134, 1234, 1234'

console.log(tel.replace(' '.The '-')) / / 134-1234, 1234
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7. replaceAll()

You can replace all qualified characters in a string with the following code:

let tel = '134, 1234, 1234'

console.log(tel.replaceAll(' '.The '-')) / / 134-1234-1234
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8. split()

The parentheses pass in what character to split, and finally return an array, which can be retrieved by subscripting the corresponding string code as follows (example) :

const hello = "Hello World";
const helloWorldSplit = hello.split(' ');

console.log(helloWorldSplit); // ["Hello", "World"];
console.log(helloWorldSplit[0]); // "Hello"
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9. substring()

Pass in two arguments, the truncated actual index and the truncated termination index code as follows (example) :

const hello = 'Hello World';

console.log(hello.substring(1.4)); // ell
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Note: the end index character is not truncated, the second parameter is not passed, the default truncation to the last character

10. toLowerCase()/toUppercase()

The code for cashing a string is as follows (example) :

const username = 'Leo'

console.log(username.toLowerCase()) // leo
console.log(username.toUpperCase()) // LEO
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11. trim()

To remove whitespace from the left and right sides of the string, invalidates Spaces in the middle of the string (example) :

const username = ' le o '

console.log(username.trim()) // le o
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12. indexOf()

The code for finding the starting position of the index value for the first occurrence of the specified string in a string is as follows (example) :

const str = 'Hi~ My name is Leo,nice to meet you~'

console.log(str.indexOf('Leo')) / / 15
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conclusion

Today concludes here ~ breaks