/数组的方法     toString(),join(),pop(),push(),shift(),unshift(),splice(),concat(),slice() 
        //1.toString()与join()一样都是把数组转成以逗号分割的字符串
        var fruits=['Banana','Orange','Apple'];        var foods=['rice']
        console.log(fruits.toString()) // Banana,Orange,Apple
        console.log(fruits.join()) // Banana,Orange,Apple


        //2.pop() 删除数组的最后一项
        var fruits=['Banana','Orange','Apple'];        var str=fruits.pop(); //str=Apple
        console.log(fruits) //['Banana','Orange']
        //3.push() 往数组最后添加新数据
        var fruits=['Banana','Orange','Apple'];        var str=fruits.push('kkk') // str=4 返回的数组的长度        
        console.log(fruits) //['Banana','Orange','Apple','kkk'];    
        
        //4.shift() 删除数组最前面的一项
        var fruits = ["Banana", "Orange", "Apple", "Mango"];        var str=fruits.shift();   //str=Banana
        console.log(fruits) //["Orange", "Apple", "Mango"];    
        //5. unshift() 往数组开头添加新数据
        var fruits = ["Banana", "Orange", "Apple", "Mango"];        var str=fruits.unshift('ll');   //str=ll
        console.log(fruits) //["ll", "Banana", "Orange", "Apple", "Mango"]
        //6. splice() 方法可用于向数组添加新项或者删除数组
        //新增
        var fruits = ["Banana", "Orange", "Apple", "Mango"];
        fruits.splice(2, 0, "Lemon", "Kiwi");
        console.log( fruits)// ["Banana", "Orange", "Lemon", "Kiwi", "Apple", "Mango"]
         //删除
        var fruits = ["Banana", "Orange", "Apple", "Mango"];
        fruits.splice(2, 1);
        console.log(fruits)// ["Banana", "Orange", "Mango"]
        //7.concat()连接两个数组生成一个新数组
        var fruits= ["Banana", "Orange", "Mango"];        var fruits1=['222'];
        console.log(fruits.concat(fruits1)) //["Banana", "Orange", "Mango", "222"]
        //8.slice()  
        var fruits = ["Banana", "Orange", "Lemon", "Apple", "Mango"];        var citrus = fruits.slice(1); 
        console.log(citrus) // (4) ["Orange", "Lemon", "Apple", "Mango"]