//apply用法
        function A(alpha,age){
            this.name = 'bob';
            alert(alpha + arguments[1] + this.name)
        }
        (function(){
            A.apply(this,['a',25])
        })()
        
        //call方法
        function B(alpha){
            this.name = 'alice';
            alert(alpha + this.name)
        }
        
        (function(){
            B.call(this,'b')
        })()
        
        //普通函數(shù)
        function love(alpha){
            this.name = 'alice';
            alert(alpha + this.name)
        }
        
        (function(){
            love.call(this,'love')
        })()
        //async函數(shù)
        async function create(alpha){
            this.name = 'op';
            var res = await compute();
            alert(alpha + this.name + res)
        }
        (function(){
            create.call(this,'b')
        })()
        //generator函數(shù)
        function * gen(num){
            console.log(num);
            num ++;
            yield 'first'
            yield 'then'
            yield 'final'
            return num
        }
        (function(){
            gen.call(this,0)
        })()
        
        let it = gen(3);

          console.log(it.next())  // {value: "first", done: false}
          console.log(it.next())   // {value: "then", done: false}
          console.log(it.next())   // {value: "final", done: false}
          console.log(it.next())   // {value: "4", done: true}
          
          
          function compute(){ 
              var num = 0;
              for(let i = 0; i < 10 ; i++){//1+2+3+4+5+ ... + 9 =>(1+9)*9/2 = 45
                  num += i;
              }
              return num
          }