# 陣列 array
## 字串不能當陣列的索引值
## 字串切割成陣列split

let str="123,456,789,asd";
let splited=str.split(",");
console.log(splited);
--------------------------------
(4) ["123", "456", "789", "asd"]
0: "123"
1: "456"
2: "789"
3: "asd"
length: 4

## 陣列組合成字串join

let studer=["wendy","sandy","coarl"];
let joined=studer.join(",");
console.log(joined);
------------------------
wendy,sandy,coarl

## 新增殖到陣列的尾巴push

let fruits=["apple","banana"];
fruits.push"group";
console.log(fruits);
----------------
["apple","banana","group"]

## 刪除和插入直到陣列中splice

splice(開始數字，刪除數量,增加新值1,增加新值2....)
從0開數，倒數從-1、。
fruits.splice(2,1,cherry,tomato);
console.log(fruits);
---------------------------
(4) ["Apple", "Banana", "cherry", "tomato"]
0: "Apple"
1: "Banana"
2: "cherry"
3: "tomato"
length: 4

## 顛倒陣列reverse

fruits.reverse();
console.log(fruits);
-------------------------
(4) ["Tomato", "Cherry", "Banana", "Apple"]
0: "Tomato"
1: "Cherry"
2: "Banana"
3: "Apple"
length: 4

## 檢查陣列中是否有包含值includes

includes回傳true、false
indexof 回傳第一個索引值沒有是-1
let haveapple=fruits.includes(Apple);
console.log(hveapple);
let haveapple1=frits.indexof(Apple);
console.log(haveapple1);
------------------------------
true
3

# forEach裡面放function
第一個是值，第二個是索引(0、1、2、3)

fruits.forEach(function(value,index){
	dw(`${value},${index}`<br>)
})
fruits.forEach((i,j)=>{
	dw(`${i},${j}<br>`);
})