A.forEachB.mapC.filterD.every
A.報錯B.console.log(x)輸出"a"C.console.log(y)輸出undefinedD.console.log(z)輸出[]
A.console.log(a)輸出1B.console.log(b)輸出2C.console.log(b)輸出[2,3]D.console.log(d)輸出4