Operation of ES6

Catalog

• var function
  • var The problem is
    • Variable promotion （ First of all , Will not copy ）
    • There is no block-level scope , Is global scope / Function scope
• let const
  • let The advantages of
    • No variable promotion , Cannot be defined repeatedly , Does not pollute global variables
    • Hui He {} Generate scope
  • let There are certain problems

let a = 2
{
  console.log(a)
  let a =1
}
// undefined

• const
  • let You can reassign const Cannot change the assigned space

const a = 1
a = 2
//  Report errors 
const b = []
b.push(1)
//  The normal operation 

• Extension operator
  • Sum any number
    • ES5 Realization slice
    • ES6... Realization
  • Merge two arrays
    • ES5 Realization concat
    • ES6... Realization
  • Merge two objects
  • The problem is （ Deep copy 、 Shallow copy ）
    • Deep copy The copy is not a reference address
    • ... Only one layer can be expanded, which is a shallow copy , It needs recursive processing
      • JSON.parse It can be solved simply
      • JSON There are certain problems
        • Can handle null/date
        • Cannot handle regular 、 function
    • Based on the above considerations, realize a deep copy ...
• Deconstruct assignment
  • Object to deconstruct
  • An array of deconstruction
• Arrow function arrowFn
  • No, this
  • No, argument
• Object.defineProperty
  • Use
  • application
    • vue2.0 Implement data bidirectional binding
  • shortcoming
    • Cannot detect array
• proxy、reflect
  • application
    • vue3.0 Rewrite data bidirectional binding
  • shortcoming
    • Poor compatibility
  • advantage
    • Can detect array
  • Deep monitoring （ It can be recursive ）（ Think for yourself ）
• class class
  • ES5 knowledge
    • proto Looking for the prototype of the class , All types
    • prototype This is the prototype , Only constructors have prototypes
    • Inherit
      • Inherit properties on instances
        • call
      • Inherit public attributes
        • Object.create
        • Child.prototype = Object.create(Parent.prototype, { constructor: { value: Child } })
        • ES5 How to achieve
      • All of them
        • call + Prototype inheritance
  • ES6 Class
    • Translate it into ES5 The appearance of
• Decorator
  • Decoration
  • Attributes in the decoration class
  • Methods in decorating classes
  • Cannot decorate functions , Because the function has variable promotion
• Set/Map
  • API List
  • Interview questions
    • The union of two arrays
    • Find the intersection of two arrays
    • Difference set of two arrays
• Array method
  • findIndex
  • reduce
    • application
      • Array sum
      • Combine compose