Add support for milliseconds resolution in timestamps to date helper

ChangeLog.md

@@ -3,6 +3,12 @@ Handlebars for XP web frontends change log
 
 ## ?.?.? / ????-??-??
 
+## 0.3.0 / 2021-02-13
+
+* Add support for milliseconds resolution in timestamps to `date` helper,
+  thus being able to use JavaScript timestamps.
+  (@thekid)
+
 ## 0.2.0 / 2021-02-13
 
 * Add `any`, `none` and `all` helpers - @thekid

README.md

@@ -52,3 +52,16 @@ On top of the [built-in functionality in Handlebars](https://github.com/xp-forge
 * `none`: Test whether none of the given arguments is truthy
 * `all`: Test whether all of the given arguments is truthy
 * `date`: Transforms dates and timestamps
+
+### Date handling
+
+The `date` helper accepts anything the `util.Date` class accepts as constructor argument, or a `util.Date` instance itself. To format the date, the `format` argument can be used with anything the `util.Date::toString()` method accepts. Here are some examples:
+
+```handlebars
+{{date "2021-02-13"}}
+{{date "13.02.2021 17:56:00"}}
+{{date 1613209181}}
+{{date 1613209181279 timestamp="ms"}}
+{{date created}}
+{{date created format="d.m.Y"}}
+```

src/main/php/web/frontend/Handlebars.class.php

@@ -79,10 +79,14 @@ public function __construct($templates) {
         return empty($options) ? 0 : 1;
       })
       ->withHelper('date', function($in, $context, $options) {
+        static $resolution= ['s' => 1, 'ms' => 1000];
+
         if (!isset($options[0])) {
           $d= Date::now();
         } else if ($options[0] instanceof Date) {
           $d= $options[0];
+        } else if ($r= $options['timestamp'] ?? null) {
+          $d= new Date('@'.($options[0] / $resolution[$r]));
         } else {
           $d= new Date($options[0]);
         }

src/test/php/web/frontend/unittest/HandlebarsTest.class.php

@@ -122,6 +122,11 @@ public function current_date($template) {
     Assert::equals(Date::now()->toString('d.m.Y'), $this->transform($template));
   }
 
+  #[Test, Values(['{{date 1613235019279 timestamp="ms"}}', '{{date 1613235019 timestamp="s"}}'])]
+  public function timestamp_resolution($template) {
+    Assert::equals('13.02.2021', $this->transform($template));
+  }
+
   #[Test, Values([['', 0], ['null', 0], ['"test"', 1], ['null "test"', 1], ['numbers', 1], ['empty', 0]])]
   public function any($expr, $expected) {
     Assert::equals((string)$expected, $this->transform('{{any '.$expr.'}}', [