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问题:

I have a Javascript in which I need to paste the current time in a format HH:MM AM/PM. There's one catch - I need to put the time that starts in two hours from now, so for example, instead of 7:23PM I need to put 9:23PM, etc.

I tried to do something like: var dateFormat = new Date("hh:mm a") but it didn't work. I also tried to use:

var today = new Date();
var time = today.toLocaleTimeString().replace(/([\d]+:[\d]{2})(:[\d]{2})(.*)/, "$1$3")
alert(time);

but all I've seen was e.g. 18:23 instead of 6:23 PM (probably because of toLocaleTimeString() and my location in Europe) - maybe there's some unified way to do that that will work all around the World?. Also, I don't know exactly how to add the 2 hours to the final result. Can you help me? Thanks!

回答1:

Use Date methods to set and retrieve time and construct a time string, something along the lines of the snippet.

[edit] Just for fun: added a more generic approach, using 2 Date.prototype extensions.

var now = new Date();
now.setHours(now.getHours()+2);
var isPM = now.getHours() >= 12;
var isMidday = now.getHours() == 12;
var result = document.querySelector('#result');
var time = [now.getHours() - (isPM && !isMidday ? 12 : 0), 
            now.getMinutes(), 
            now.getSeconds() || '00'].join(':') +
           (isPM ? ' pm' : 'am');
            
result.innerHTML = 'the current time plus two hours = '+ time;

// a more generic approach: extend Date
Date.prototype.addTime = addTime;
Date.prototype.showTime = showTime;

result.innerHTML += '<h4>using Date.prototype extensions</h4>';
result.innerHTML += 'the current time plus twenty minutes = '+ 
                      new Date().addTime({minutes: 20}).showTime();
result.innerHTML += '<br>the current time plus one hour and twenty minutes = '+ 
                      new Date().addTime({hours: 1, minutes: 20}).showTime();
result.innerHTML += '<br>the current time <i>minus</i> two hours (format military) = '+ 
                      new Date().addTime({hours: -2}).showTime(true);
result.innerHTML += '<br>the current time plus ten minutes (format military) = '+ 
                      new Date().addTime({minutes: 10}).showTime(true);


function addTime(values) {
  for (var l in values) {
    var unit = l.substr(0,1).toUpperCase() + l.substr(1);
    this['set' + unit](this['get' + unit]() + values[l]);
  }
  return this;
}

function showTime(military) {
  var zeroPad = function () {
    return this < 10 ? '0' + this : this;
  };
  
  if (military) {
    return [ zeroPad.call(this.getHours()),
             zeroPad.call(this.getMinutes()),
             zeroPad.call(this.getSeconds()) ].join(':');
  }
  var isPM = this.getHours() >= 12;
  var isMidday = this.getHours() == 12;
  return time = [ zeroPad.call(this.getHours() - (isPM && !isMidday ? 12 : 0)),
                  zeroPad.call(this.getMinutes()),
                  zeroPad.call(this.getSeconds()) ].join(':') +
                (isPM ? ' pm' : ' am');

  
 
}

<div id="result"></div>

回答2:

You can convert the current time to 12 hour format with a one liner

new Date().toLocaleTimeString('en-US', { hour: 'numeric', hour12: true, minute: 'numeric' });

And to add two hours to your current time

Date.now() + 2 * 60 * 60 * 1000

So you can do it in a simple one line as:

new Date(Date.now() + 2 * 60 * 60 * 1000).toLocaleTimeString('en-US', { hour: 'numeric', hour12: true, minute: 'numeric' });

回答3:

Note that the accepted answer, while good, does not appear to meet the format requirement of: HH:MM AM/PM. It returns midnight as "0:0:38am" and so forth.

There are many ways one could do this and one alternative is shown below. Click the "Run Code Snippet" to test.

<!DOCTYPE HTML>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<title>Clock</title>
</head>
<body>
<span id="clock"  style="font-family: monospace; font-size: 48px; background-color: black; color: lime; padding: 10px;">00:00:00 AM</span>
<script type="text/javascript">

function getTime( ) {
	var d = new Date( ); 
	d.setHours( d.getHours() + 2 ); // offset from local time
	var h = (d.getHours() % 12) || 12; // show midnight & noon as 12
	return (
		( h < 10 ? '0' : '') + h +
		( d.getMinutes() < 10 ? ':0' : ':') + d.getMinutes() +
                // optional seconds display
		// ( d.getSeconds() < 10 ? ':0' : ':') + d.getSeconds() + 
		( d.getHours() < 12 ? ' AM' : ' PM' )
	);
	
}

var clock = document.getElementById('clock');
setInterval( function() { clock.innerHTML = getTime(); }, 1000 );
</script>
</body>
</html>

回答4:

This should work.

var date = new Date();
var hour = date.getHours() - (date.getHours() >= 12 ? 12 : 0);
var period = date.getHours() >= 12 ? 'PM' : 'AM';

alert( hour + 2 + ':' + date.getMinutes() + ' ' +period);