client/home: format absolute time

client/js/util/misc.js

@@ -0,0 +1,44 @@
+'use strict';
+
+function formatRelativeTime(timeString) {
+    if (!timeString) {
+        return 'never';
+    }
+
+    const then = Date.parse(timeString);
+    const now = Date.now();
+    const difference = Math.abs(now - then) / 1000.0;
+    const future = now < then;
+
+    const descriptions = [
+        [60,                            'a few seconds', null],
+        [60 * 2,                        'a minute',      null],
+        [60 * 60,                       '% minutes',     60],
+        [60 * 60 * 2,                   'an hour',       null],
+        [60 * 60 * 24,                  '% hours',       60 * 60],
+        [60 * 60 * 24 * 2,              'a day',         null],
+        [60 * 60 * 24 * 30.42,          '% days',        60 * 60 * 24],
+        [60 * 60 * 24 * 30.42 * 2,      'a month',       null],
+        [60 * 60 * 24 * 30.42 * 12,     '% months',      60 * 60 * 24 * 30.42],
+        [60 * 60 * 24 * 30.42 * 12 * 2, 'a year',        null],
+        [8640000000000000 /*max*/, '% years', 60 * 60 * 24 * 30.42 * 12],
+    ];
+
+    let text = null;
+    for (let kv of descriptions) {
+        const multiplier = kv[0];
+        const template = kv[1];
+        const divider = kv[2];
+        if (difference < multiplier) {
+            text = template.replace(/%/, Math.round(difference / divider));
+            break;
+        }
+    }
+
+    if (text === 'a day') {
+        return future ? 'tomorrow' : 'yesterday';
+    }
+    return future ? 'in ' + text : text + ' ago';
+}
+
+module.exports = {formatRelativeTime: formatRelativeTime};