用JS显示9天的数字

I'm trying to display 9 day numbers with js.

With PHP it will look like this:

for($i = 0; $i < 4; $i++){
    $date = new DateTime();
    $date->sub(new DateInterval('P'.(4 - $i).'D'));
    echo '<span class="day_nr">'.$date->format('d').'</span>';
}

$date = new DateTime();
echo '<span class="selected_day_nr day_nr">'.$date->format('d').'</span>';

for($i = 1; $i < 5; $i++){
    $date = new DateTime();
    $date->add(new DateInterval('P'.$i.'D'));
    echo '<span class="day_nr">'.$date->format('d').'</span>';
}

This is what i have found in JS:

var date = new Date();
date.setDate(date.getDate() + 1); console.log(date)

But this will show the whole date like: Wed Feb 21 2018 11:23:30 GMT+0100 (CET)

How do i display it with only the day number? (21)

You can use .getDate() to get the date of the month represented by the Date object. For example:

var date = new Date();
date.setDate(date.getDate() + 1); console.log(date.getDate())

To emulate PHP's P option, a good starting point would be date.getTimezoneOffet(), however this will not include proper formatting as with PHP.

For more information, take a look at the docs. You may also find this list a little more helpful.

Thank to @Toastrackenigma for (.getDate())

This is how the loop works:

//4 days back
var date = new Date();
for(i = -4; i < 0; i++){
    var date = new Date();
    date.setDate(date.getDate() + i);
    $('.panel-body .row .cold-12').append('<span class="day_nr">'+date.getDate()+'</span>');
}

//Today
var date = new Date(); 
$('.panel-body .row .cold-12').append('<span class="selected_day_nr day_nr">'+date.getDate()+'</span>');

//4 days forward
var date = new Date();
for(i = 1; i < 5; i++){
    var date = new Date();
    date.setDate(date.getDate() + i);
    $('.panel-body .row .cold-12').append('<span class="day_nr">'+date.getDate()+'</span>');
}

Console: -4 days, +4 days

As said previously by Toastrackenigma you can use: getDate () to retrieve only what you want. But for the manipulation of the dates I can advise you the awesome library : https://momentjs.com/ which is really useful.