JS 循環改變值

1.arr=[{age:12},{age:18}]

arr.forEach(t=>t.age=t.age*2)
undefined
arr
{age: 24}1: {age: 36}   length: 2__proto__: Array(0)

改變了值

2.數值和string 不會改變值

var numbers = [4, 9, 16, 25];
numbers.forEach(t=>t=t*3)

結果  numbers ： [4, 9, 16, 25]

arr=["22","safas","afsaf"]
arr.forEach(t=>t=t+"safasf")
結果 arr=["22", "safas", "afsaf"]