订阅和推送后无法使用 Array.toString()

Question

这是一段有问题的代码：

const arr1 = new Array;

this.formData.players.split(',').forEach((id) => {
  this.userService.getUser(Number(id)).subscribe((user: User) => {
    arr1.push(user.firstname + ' ' + user.lastname);
  });
});

console.log(arr1);
console.log('Players: ' + arr1.join(', '));

/* - - - - - */

const arr2 = new Array;

arr2.push('orange');
arr2.push('mango');
arr2.push('banana');
arr2.push('sugar');

console.log(arr2);
console.log('Test: ' + arr.join(', '));

第一部分从 Spring 数据库中获取用户的身份。第二个用于测试。

我的日志：

[]
  0: "John Doe"
  1: "Jane Doe"
  length: 2
  __proto__: Array(0)

Players:

(4) ["orange", "mango", "banana", "sugar"]
  0: "orange"
  1: "mango"
  2: "banana"
  3: "sugar"
  length: 4
  __proto__: Array(0)

Test: orange, mango, banana, sugar

我不明白为什么我的第一段代码拒绝显示：

Players: John Doe, Jane Doe

Answer 1

我认为这是因为您的 console.log 函数将在所有订阅完成之前被调用。

You can try to use something like https://www.learnrxjs.io/learn-rxjs/operators/combination/mergeall instead.

from(this.formData.players.split(',')).pipe(
  map(id => this.userService.getUser(Number(id)).pipe(tap(user: User) => {
    arr1.push(user.firstname + ' ' + user.lastname);
  })),
  mergeAll()
).subscribe((data) => {
  console.log(arr1);
  console.log('Players: ' + arr1.join(', '));
});