扩展运算符仅将for循环中的最后一个值相加

let result = [];
for (let i = 0; i < arr.length; i++) {
  result.push(...arr[i]);
}
console.log(result);

let result = [];
let promises = [];

for (let i = 0; i < arr.length; i++) {
  promises.push(new Promise((resolve) => {
    resolve(arr[i]);
  }));
}

Promise.all(promises).then((values) => {
  values.forEach((value) => {
    result.push(...value);
  });
  console.log(result);
});

let result = [];
for (let i = 0; i < arr.length; i++) {
  result.push(...arr[i]);
}
console.log(result);

let arr = [
  [1, 2, 3],
  [4, 5, 6],
  [7, 8, 9]
];

let result = [];
for (let i = 0; i < arr.length; i++) {
  result.push(...arr[i]);
}
console.log(result); // 输出: [1, 2, 3, 4, 5, 6, 7, 8, 9]