數組頭部，尾部添加數據和刪除指定位置下標的元素

//unshift() 方法可向數組的開頭添加一個或更多元素，並返回新的長度。
//將新項添加到數組起始位置:
var fruits = ["Banana", "Orange", "Apple", "Mango"];
fruits.unshift("Lemon","Pineapple");
//將新項添加到數組末尾位置:
var fruits = ["Banana", "Orange", "Apple", "Mango"];
fruits.push("Lemon","Pineapple");
//刪除數據
let arr = ["james","irving","kobe","wade"];
arr.splice(1,1) //在下標1處開始刪除,刪除一位
console.log(arr);// irving被刪除