Arrow function of new features of ES6

summary ：ES6 Arrows are allowed （=>） Defined function , Arrow functions provide a more concise way to write functions , Arrow functions are often used to define anonymous functions ;

Note on arrow function

• If there is only one parameter , Then brackets can be omitted
• If there is only one statement in the function body , The curly braces can be omitted
• Arrowhead function this Refers to the this value
• Arrow functions cannot be instantiated as constructors
• Out of commission arguments

The properties of the arrow function

• Arrowhead function this Is static , Always point to this value
• Cannot instantiate an object as a construct
• Out of commission arguments Variable

Code demonstration
The traditional way of writing

 	var sayHi = function(){
    
        console.log(" hello ! Xiao Liu ");
    }
    sayHi()
    //  Running results : hello ! Xiao Liu 

ES6 How to write it ： No parameter

   let speak = ()=>console.log("hello  ha-ha !");
    speak()
    //  Running results :hello  ha-ha !

The traditional way of writing One parameter

	var hello = function(name){
    
        return ` hello ！${
      name}`
    }
    console.log(hello(" Xiao Liu "));
     //  Running results : hello ！ Xiao Liu 

ES6 Arrow function : One parameter

	let Hi = name => `hello${
      name}`
    console.log(Hi(" Xiao Liu "));
    //  Running results :hello Xiao Liu 

The traditional way of writing ： Multiple parameters

 	var sum = function(a,b,c){
    
        return a+b+c
    }
    console.log(sum(1,2,3));
    // Running results :6 

ES6 How to write it Multiple parameters

 	let add = (a,b,c)=>a + b + c
    console.log(add(6,7,8));
    //  Running results :21

Feature case demonstration

 Arrowhead function this Is static , Always point to... Under the scope where the function is declared this Value 

  const school = {
    
        call:" hello !",
        name:" Xiao Liu "
    }
    //  Traditional functions 
    function sayHiName(){
    
        console.log(this.call+this.name);
    }
    //  Arrow function 
    let sayHiName1 = ()=>{
     console.log(this.call+this.name);}

    window.name = " Xiao Zhang "

    //  Call directly 
    sayHiName()
    // undefined Xiao Zhang 
    sayHiName1()
    // undefined Xiao Zhang 

Use call call

  	sayHiName.call(school)
    //  hello ! Xiao Liu 
    sayHiName1.call(school)
    // undefined Xiao Zhang 
    //  summary : Arrowhead function this Is static , Always point to... Under the scope where the function is declared this Value 

 Cannot instantiate an object as a construct 

  let Person = (name,age) =>{
    
        this.name = name
        this.age = age
    }

    let me = new Person(" Xiao Zhang ",24)
    console.log(me);
    // Report errors :t TypeError: Person is not a constructor

 Out of commission arguments  Variable 

  let fn = () =>console.log(argument);
    fn(1,2,3)
    //  Report errors  argument is not defined