Add utilities for transforming duration objects

lib/www/client/source/src/lib/durations.js

@@ -0,0 +1,47 @@
+
+function duration_to_ms(v) {
+  if (v instanceof Object) {
+    return (
+      (v.days || 0) * 86400000 +
+      (v.hours || 0) * 3600000 +
+      (v.minutes || 0) * 60000 +
+      (v.seconds || 0) * 1000 +
+      (v.milliseconds || 0)
+    );
+  } else {
+    return {
+      days: 0,
+      hours: 0,
+      minutes: 0,
+      seconds: 0,
+      milliseconds: 0
+    }
+  }
+}
+
+function ms_to_duration(v) {
+  const days = Math.floor(v / 86400000);
+  v %= 86400000;
+  const hours = Math.floor(v / 3600000);
+  v %= 3600000;
+  const minutes = Math.floor(v / 60000);
+  v %= 60000;
+  const seconds = Math.floor(v / 1000);
+  const milliseconds = v % 1000;
+  return { days, hours, minutes, seconds, milliseconds };
+}
+
+function normalise_duration (v) {
+  return ms_to_duration(duration_to_ms(v));
+}
+
+function add_durations(a, b) {
+  return ms_to_duration(duration_to_ms(a) + duration_to_ms(b));
+}
+
+export {
+  duration_to_ms,
+  ms_to_duration,
+  normalise_duration,
+  add_durations
+}