js这个要怎么运算的啊

var list = [1,2,3,4,5,6,7,8,9]
for (let i = 0; i < list.length; i++) {
  if(i % 2 == 0) {
    list[i] = list[i] * 10
  } else {
    list[i] = 0
  }
}
console.log(list);

list.forEach(item=>{
if(item%2===0){
item = item * 10
}else{
item = 0
}
})