Summary of commonly used string methods in js and es6 (collection)

Commonly used strings in js and es6, for example: slice(start,end) -> Intercept string, usage: The usage of slice is basically the same as the usage of substring, but the difference is: 1.slice(start,end ) -> start cannot be greater than end, otherwise an empty string will be returned;
2.slice can accept a negative number as a parameter. If it is a negative number, the rules will be as follows: add the length of the string and the assignment, and replace this Value

1.substring(start,end) -> Intercept string

Usage:

1.substring(start,end) -> Use To express a range in a mathematical expression, intercept [start, end);
2.substring(start,end),end > start -> The same result as above will be automatically switched, but both start and end must be is a positive number. If both start and end are empty, return the original string (meaningless)
3.substring(start) -> Without end, it is equivalent to [start, the last character]

let str = 'Hello world';
let use1 = str.substring(0, 3);
console.log(use1); // Hel
let use2 = str.substring(3,0);
console.log(use2); // hel
let use3 = str.substring(2);
console.log(use3); // llo world

2. slice(start,end) -> Intercept string

Usage:

The usage of slice is basically the same as that of substring, the only difference is:
1.slice( start, end) -> start cannot be greater than end, otherwise an empty string will be returned;
2.slice can accept a negative number as a parameter. If it is a negative number, the rules will be as follows: add the length of the string and the assigned value, Replace this value. For example:

let str = 'abcdefg' // length = 7
str.slice(1,-4) // bc  -> str.slice(1,7-4) -> str.slice(1,3)

3.substr(start,length) -> Intercept the string at the specified position and length

Usage:

1.substr(start,length) -> The intercepted string interval is: [start,start length)->Start from start, count the number of start and length strings;
2 .substr(start) -> The intercepted string interval is: [start, last character]

  let str = 'Hello world';
  console.log(str.substr(1,2)) // el
  console.log(str.substr(3)) // lo world

4.split()

5.indexOf(char,index ) and lastIndexOf(char,index)

1.char: is the character you are looking for, index: is the position number of the character to start looking for (if not, it is the leftmost character in indexOf, in lastIndexOf is the rightmost character);
2. indexOf searches from left to right, while lastIndexOf searches from right to left;
3. Their return values ​​are all the position numbers where the char is found, If not found, return -1

  let str = 'good';
  console.log(str.indexOf('o')); // 1
  console.log(str.lastIndexOf('o')); // 2

6.charAt(index) and charCodeAt(index) and at(index) (es6 attribute)

charAt(index) returns the character at index position , charCodeAt(index) returns the character Unicode code at index position
charAt(index) cannot recognize characters greater than 0xFFFF. At this time, you can use at() to identify

  var str = 'abc'
  str.charAt(0) // a
  str.charCodeAt(0) // 97

Related articles:

Detailed explanation of string templates in ES6

Analysis of the representation methods of multi-line strings and connection strings in ES6 and related operation skills

Related Video:

Javascript - ES6 Practical Video Course - Free Online Video Tutorial

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