map方法的應用

var data = [
{id: 1, name: "張三", age: 29, constellation: "水瓶座"},
{id: 2, name: "李四", age: 17, constellation: "射手座"},
{id: 3, name: "王五", age: 34, constellation: "白羊座"},
{id: 4, name: "趙六", age: 18, constellation: "金牛座"},
{id: 5, name: "孫七", age: 22, constellation: "巨蟹座"},
{id: 6, name: "周八", age: 25, constellation: "摩羯座"},
{id: 7, name: "吳九", age: 31, constellation: "雙子座"}
]

如何取出所有星座並組成一個新的數組？

var newData = data.map(function(v){
   return  v.constellation
})

console.log(newData)

(7) ["水瓶座", "射手座", "白羊座", "金牛座", "巨蟹座", "摩羯座", "雙子座"]

注意：map方法有返回值 forEach沒有返回值