javascript - 使用momentjs显示当前时间

Question

我正在尝试创建一个动态显示当前时间的时钟组件。

Problem: Time is shown as expected on load (HH:mm A), but the clock does not change at all.

clock.component.ts:

import {
    ChangeDetectionStrategy,
    Component,
    OnInit
} from "@angular/core";
import { Observable, interval } from "rxjs";
import { map, distinctUntilChanged } from "rxjs/operators";
import * as moment from "moment";

@Component({
    selector: "app-clock",
    templateUrl: "./clock.component.html",
    changeDetection: ChangeDetectionStrategy.OnPush
})
export class ClockComponent implements OnInit {

    pageLoaded: moment.Moment;
    time: Observable<string>;

    constructor() {}

    ngOnInit() {
        this.pageLoaded = moment(new Date());

        this.time = interval(1000).pipe(
            map(() => this.pageLoaded.format("HH:mm A")),
            distinctUntilChanged()
        );
    }
}

clock.component.html:

<div>{{ time | async }}</div>

Answer 1

首先，如果我在你身边，我将使用 @types/moment 让我的生活更轻松(可选)。

那么，为什么“时钟根本没有改变”？

因为您在页面加载后初始化了时钟的值，并且该值不会更新，所以基本上 this.time 保存的是初始化值，而不是更新后的值，因此，以下是与您的组件相同，但版本较小。

import {
    ChangeDetectionStrategy,
    Component,
    OnInit
} from "@angular/core";
import { Observable, interval } from "rxjs";
import { map, distinctUntilChanged } from "rxjs/operators";
import moment, { Moment } from "moment"; // using @types/moment

@Component({
    selector: "app-clock",
    templateUrl: "./clock.component.html",
    changeDetection: ChangeDetectionStrategy.OnPush
})
export class ClockComponent implements OnInit {

    pageLoaded: Moment;
    time: Observable<string>;

    constructor() {}

    ngOnInit() {
    this.time = interval(1000*60).pipe( // why you need 1s interval with HH:mm time format simply update it every minute not every second.
      map(() => {
        this.pageLoaded = moment(new Date()); // you need the value of now not the value of the initialized time.
        return this.pageLoaded.format("HH:mm A");
      })
    );
  }
}

以及您的 View 本来的样子。

这是一个 stackblitz 示例，请自行检查 https://stackblitz.com/edit/angular-moment-rxjs