//1.返回值 最常用的
    function fn(){
        var name="hello";
        return function(){
            return name;
        }
    }
    var fnc = fn();
    console.log(fnc())//hello

var fn2;
function fn(){
    var name="hello";
    //將函數(shù)賦值給fn2
    fn2 = function(){
        return name;
    }
}
fn()//要先執(zhí)行進行賦值，
console.log(fn2())//執(zhí)行輸出fn2

function fn(){
    var name="hello";
    return function callback(){
        return name;
    }
}
var fn1 = fn()//執(zhí)行函數(shù)將返回值（callback函數(shù)）賦值給fn1，
 
function fn2(f){
    //將函數(shù)作為參數(shù)傳入
    console.log(f());//執(zhí)行函數(shù)，并輸出
}
fn2(fn1)//執(zhí)行輸出fn2

(function(){
        var name="hello";
        var fn1= function(){
            return name;
        }
        //直接在自執(zhí)行函數(shù)里面調用fn2，將fn1作為參數(shù)傳入
        fn2(fn1);
    })()
    function fn2(f){
        //將函數(shù)作為參數(shù)傳入
        console.log(f());//執(zhí)行函數(shù)，并輸出
    }

//每秒執(zhí)行1次，分別輸出1-10
for(var i=1;i<=10;i++){
    (function(j){
        //j來接收
        setTimeout(function(){
            console.log(j);
        },j*1000);
    })(i)//i作為實參傳入
}

function fn(){
        var name="hello"
        setName=function(n){
            name = n;
        }
        getName=function(){
            return name;
        }
         
        //將setName，getName作為對象的屬性返回
        return {
            setName:setName,
            getName:getName
        }
    }
    var fn1 = fn();//返回對象，屬性setName和getName是兩個函數(shù)
    console.log(fn1.getName());//getter
        fn1.setName("world");//setter修改閉包里面的name
    console.log(fn1.getName());//getter

var arr =["aa","bb","cc"];
function incre(arr){
    var i=0;
    return function(){
        //這個函數(shù)每次被執(zhí)行都返回數(shù)組arr中 i下標對應的元素
         return arr[i++] || "數(shù)組值已經遍歷完";
    }
}
var next = incre(arr);
console.log(next());//aa
console.log(next());//bb
console.log(next());//cc
console.log(next());//數(shù)組值已經遍歷完

var fn = (function(){
               var arr=[];//用來緩存的數(shù)組
                   return function(val){
                       if(arr.indexOf(val)==-1){//緩存中沒有則表示需要執(zhí)行
                           arr.push(val);//將參數(shù)push到緩存數(shù)組中
                           console.log("函數(shù)被執(zhí)行了",arr);
                           //這里寫想要執(zhí)行的函數(shù)
                       }else{
                           console.log("此次函數(shù)不需要執(zhí)行");
                       }
                       console.log("函數(shù)調用完打印一下，方便查看已緩存的數(shù)組：",arr);
                   }
               })();
        
       fn(10);
       fn(10);
       fn(1000);
       fn(200);
       fn(1000);

//比如求和操作，如果沒有緩存，每次調用都要重復計算，采用緩存已經執(zhí)行過的去查找，查找到了就直接返回，不需要重新計算
      
     var fn=(function(){
        var cache={};//緩存對象
        var calc=function(arr){//計算函數(shù)
            var sum=0;
            //求和
            for(var i=0;i<arr.length;i++){
                sum+=arr[i];
            }
            return sum;
        }
         
        return function(){
            var args = Array.prototype.slice.call(arguments,0);//arguments轉換成數(shù)組
            var key=args.join(",");//將args用逗號連接成字符串
            var result , tSum = cache[key];
            if(tSum){//如果緩存有   
                console.log("從緩存中取：",cache)//打印方便查看
                result = tSum;
            }else{
                //重新計算，并存入緩存同時賦值給result
                result = cache[key]=calc(args);
                console.log("存入緩存：",cache)//打印方便查看
            }
            return result;
        }
     })();
    fn(1,2,3,4,5);
    fn(1,2,3,4,5);
    fn(1,2,3,4,5,6);
    fn(1,2,3,4,5,8);
    fn(1,2,3,4,5,6);