javascript - arr.push(arr.splice(n,1)) "swallows"被移动对象的属性

Question

例如，我想把中间的元素放到最后:

let students=[
    {"name":"a","uid":"001"},
    {"name":"b","uid":"002"},
    {"name":"c","uid":"003"},
    {"name":"d","uid":"004"},
    {"name":"e","uid":"005"},
];
students.push(students.splice(students.length/2,1));
console.log(students.length);
for(let s of students){
  console.log(s.name+':'+s.uid+',');
}

尽管元素数量不变，但最后一个元素的属性变得未定义，为什么会发生这种情况？

Answer 1

splice 始终返回一个数组，即使只删除一个元素也是如此。如果您想推送已删除的student，则必须先将其从数组中提取出来，否则您将向students推送数组> (而不是学生对象):

let students=[
    {"name":"a","uid":"001"},
    {"name":"b","uid":"002"},
    {"name":"c","uid":"003"},
    {"name":"d","uid":"004"},
    {"name":"e","uid":"005"},
];
const [student] = students.splice(students.length/2,1);
students.push(student);
// or
// students.push(students.splice(students.length/2,1)[0]);
console.log(students.length);
for(let s of students){
  console.log(s.name+':'+s.uid+',');
}