我們在寫程式時陣列是很常用到的東西，我們來看看js有提供那些方法來對陣列做改動。

type

typeof(obj)，可得知obj的型態，會輸出string、number、boolean、object等....。

text:"asd",

console.log(typeof(this.text))//輸出string

length

可以用來判斷字串或陣列的長度

originarray:["one","two","three","four","five","six"],

console.log(this.originarray.length)//輸出6

text:"asd"

console.log(this.text.length)//輸出3

push

對指定的陣列增加值，從該陣列的最後一筆開始新增。

arraytest:["new"]

this.arraytest.push("pushtest")
console.log(this.arraytest)//輸出["new","pushtest"]

unshift

對指定的陣列增加值，從該陣列的第一筆開始新增。

arraytest:["new"]

this.arraytest.unshift("unshifttest")
console.log(this.arraytest)//輸出["unshifttest",new"]

includes

判斷陣列有無指定值，若有回傳true，若否回傳false。

originarray:["one","two","three","four","five","six"],

console.log(this.originarray.includes("two"))//輸出true

也可傳入參數，表示從該陣列的索引值開始尋找。

console.log(this.originarray.includes("two",2))//輸出false

console.log(this.originarray.includes("two",1))//輸出true

indexof

判斷陣列有無指定值，若有回傳大於等於0的數值，該數值表示陣列的索引值，若否回傳-1。

originarray:["one","two","three","four","five","six"],

console.log(this.originarray.indexOf("three"))//輸出2

可傳入參數，表示從該陣列的索引值開始尋找。

console.log(this.originarray.indexOf("three",2))//輸出2
console.log(this.originarray.indexOf("three",3))//輸出-1

reverse

將陣列做反轉。

originarray:["one","two","three","four","five","six"],

console.log(this.originarray)
//輸出["one", "two", "three", "four", "five", "six"]


console.log(this.originarray.reverse())
//輸出["six", "five", "four", "three", "two", "one"]