Enter ES6 new standard syntax

• Chapter1 ECMAScript6 variable declaration
• 1-1 The relationship between ECMAScript and JavaScript
• 1-2 Examples to explain the shortcomings of using var to declare variables
• 1-3 Advantages of using let to declare variables
• 1-4 const named constant declaration
• Chapter2 Classic applications of ES6 arrow functions
• 2-1 Detailed explanation of es6 arrow function
• 2-2 Classic applications of arrow functions
• 2-3 The inheritance relationship of this in arrow functions
• Chapter3 ES6 array processing and destructuring assignment
• 3-1 New advanced methods for es6 array processing
• 3-2 Use of es6 template strings
• 3-3 Application of es6 destructuring assignment
• 3-4 es6 spread operator
• Chapter4 The concept of ES6 classes and Module modular programming
• 4-1 es6--The concept of Class class
• 4-2 es6--JSON object serialization and deserialization
• 4-3 Advantages of Module modular programming 01
• 4-4 Advantages of Module modular programming 02