Question

在我的角度应用程序中，我需要检查当前时间是否大于3PM。我正在使用Date.now（）来获取当前时间，并且在构造函数中已经拥有了，所以我会获取每分钟的更新时间，

 setInterval(() => {
            this.today = Date.now();           
          }, 1);

现在我需要检查当前时间是否大于3 PM。

Answer 1

我使用getHours()来获取一天中的时间。它将返回0到23之间的范围；因此，15为您正在寻找的下午3点。

1000*60也是1分钟的时间（以毫秒为单位）。

setInterval(() => {
  this.today = new Date();
  if (this.today.getHours() >= 15){
    console.log('Current time is greater than 3 PM!');
  }
}, 1000*60);

Answer 2

我将使用setTimeout方法来设置警报，而不是进行间隔测试。

当我们知道何时完成计算时，就不会浪费时间间隔计算。

// ES6 CLASS
class Alert {
  constructor(timestamp) {
    this.timestamp = timestamp;
    this._passed = false;
    this.callbacks = [];
    // Test as soon as possible
    setTimeout(this.test.bind(this), 0);
  }
  get passed() {
    return this._passed;
  }
  test() {
    if (this.timestamp.getTime() <= Date.now()) {
      //Test again after time difference mark as passed
      this._passed = true;
      //Fire all callbacks
      this.callbacks.forEach(cb => cb());
    } else {
      //Test again after time difference
      setTimeout(this.test.bind(this), this.timestamp.getTime() - Date.now());
    }
    return this;
  }
  then(callback) {
    if (this._passed) {
      callback();
    } else {
      this.callbacks.push(callback);
    }
    return this;
  }
}
//TEST
// Fire in 10 seconds
new Alert(new Date(Date.now() + 5 * 1000))
  .then(a => console.log("5 seconds passed"))
  .then(a => console.log("The 5 seconds were great!"));
// Fire in 4 seconds
new Alert(new Date(Date.now() + 2 * 1000))
  .then(a => console.log("2 seconds passed"))
  .then(a => console.log("The 2 seconds were meh!"));
var threeOClock = new Date();
threeOClock.setHours(15, 0, 0);
new Alert(threeOClock)
  .then(a => console.log("It's 15 or more!"));

p {
  margin: 200px 0px;
}

<pre>// TYPESCRIPT CLASS
class Alert {
    constructor(timestamp) {
        this.timestamp = timestamp;
        this._passed = false;
        this.callbacks = [];
        // Test as soon as possible
        setTimeout(this.test.bind(this), 0);
    }
    get passed() {
        return this._passed;
    }
    test() {
        if (this.timestamp.getTime() &lt;= Date.now()) {
            //Test again after time difference mark as passed
            this._passed = true;
            //Fire all callbacks
            this.callbacks.forEach(cb =&gt; cb());
        }
        else {
            //Test again after time difference
            setTimeout(this.test.bind(this), this.timestamp.getTime() - Date.now());
        }
        return this;
    }
    then(callback) {
        if (this._passed) {
            callback();
        }
        else {
            this.callbacks.push(callback);
        }
        return this;
    }
}
//TEST
// Fire in 10 seconds
new Alert(new Date(Date.now() + 5 * 1000))
    .then(a =&gt; console.log("5 seconds passed"))
    .then(a =&gt; console.log("The 5 seconds were great!"));
// Fire in 4 seconds
var fourSecondAlert = new Alert(new Date(Date.now() + 2 * 1000))
    .then(a =&gt; console.log("2 seconds passed"))
    .then(a =&gt; console.log("The 2 seconds were meh!"));
</pre>

编辑1-承诺

如果您对诺言感到满意并且只需要一个简单的警报，则应该这样做：

function Alert(date) {
  return new Promise(function(res) {
    if (Date.now() >= date.getTime()) {
      res();
    } else {
      setTimeout(res, date.getTime() - Date.now());
    }
  });
}
//TEST
Alert(new Date(Date.now() + 5 * 1000))
  .then(a => console.log("5 seconds passed"))
  .then(a => console.log("The 5 seconds were great!"));
Alert(new Date(Date.now() + 2 * 1000))
  .then(a => console.log("2 seconds passed"))
  .then(a => console.log("The 2 seconds were meh!"));
var threeOClock = new Date();
threeOClock.setHours(15, 0, 0);
Alert(threeOClock)
  .then(a => console.log("It's 15 or more!"));

创建日期对象并设置时间

创建时间戳的最简单方法是创建Date对象并使用setHours对其进行修改：

var threeOClock = new Date();
threeOClock.setHours(15, 0, 0);
console.log(threeOClock.toTimeString());

Answer 3

要检查当前时间是否大于3 PM，最好的方法是使用力矩库。请看看它是如何完成的here

Typescript中的角度时间比较

3 个答案: