如何將多個數組合並成一個數組：
concat：連接兩個或多個數組
例：arr1連接arr2
var arr1 = ['q','w']
var arr2 = ['e','r']
var arr3 = [1,2]
console.log(arr1.concat(arr2))
輸出：["q", "w", "e", "r"]
例：arr1連接arr3
var arr1 = ['q','w']
var arr2 = ['e','r']
var arr3 = [1,2]
console.log(arr1.concat(arr3))
輸出：["q", "w", 1, 2]
例：arr1連接arr2,arr3
var arr1 = ['q','w']
var arr2 = ['e','r']
var arr3 = [1,2]
console.log(arr1.concat(arr2,arr3))
輸出：["q", "w", "e", "r", 1, 2]