SOURCE

//延展操作符...可以在函数调用/数组构造时, 将数组表达式或者string在语法层面展开；
//还可以在构造对象时, 将对象表达式按key-value的方式展开。
let obj=['one','two','three'];
let objClone = [...obj ];
obj.push('four');//数组末尾插入一个元素
console.log(obj);// ["one","two","three","four"]
console.log(objClone);//> ["one","two","three"]

console.log('移除第一个元素');
let deleteItem=obj.shift();//移除第一个元素
console.log(deleteItem)//one 移除的元素内容
console.log(obj)// ["two","three","four"] 移除后的数组内容

obj.push('one');//数组末尾插入一个元素one
console.log(obj.sort());// ["four","one","three","two"] 按照字母表顺序排序
console.log(obj);//排序后的内容 ["four","one","three","two"]

console.log(obj.pop());//删除最后一个元素 two
console.log(obj);//删除后的结果打印  ["four","one","three"]


var fruits = ["Banana", "Orange", "Apple", "Mango"];
fruits.splice(2, 1, "Lemon", "Kiwi");//在第2个索引位置删除一个元素 然后添加两个元素"Lemon", "Kiwi"
console.log(fruits);// ["Banana","Orange","Lemon","Kiwi","Mango"]

//将两个数组连起来 1、使用concat 2、使用延展操作符...
let numobj=['one','two','three'];
console.log(fruits.concat(numobj));//["Banana","Orange","Lemon","Kiwi","Mango","one","two","three"]
let numobj1=['one','two','three',...fruits];
console.log(numobj1);

var arr = [1, 2, 3];
var arr2 = [...arr]; // 等同于 arr.slice()
arr2.push(4); 
console.log(arr2)//[1, 2, 3, 4]