feat: add toLocalISOString()

README.md

@@ -8,6 +8,13 @@ in ~100 LoC. For Node.js & Browsers.
 XTZ is a poor man's `Temporal` polyfill, but just for time zones. \
 Demo: <https://therootcompany.github.io/tz.js/>
 
+```js
+// What's the current time, in ISO format?
+
+TZ.toLocalISOString(new Date()); // "2021-11-07T03:15:59.000-0500"
+TZ.timeZone(); // "America/New_York"
+```
+
 > What UTC time will it be when it's 3:15am in New York?
 
 ```js
@@ -98,6 +105,7 @@ https://www.youtube.com/playlist?list=PLxki0D-ilnqa6horOJ2G18WMZlJeQFlAt
 
 # API
 
+- `toLocalISOString(dateOrNull)`
 - `toTimeZone(utcDate, timeZone)`
 - `toTimeZoneISOString(isoString, timeZone)`
 - `toUTC(dtString, timeZone)`

index.html

@@ -86,6 +86,18 @@ String(((new Date()).getTimezoneOffset() % 60)).padStart(2, '0')</code></pre>
 
     <hr />
 
+    <form class="js-local">
+      <h3>Local ISO+Offset String:</h3>
+      <pre><code>XTZ.toLocalISOString(new Date())</code></pre>
+      <label>
+        ISO:
+        <input class="js-my-dt-local" type="text" disabled />
+      </label>
+      <br />
+    </form>
+
+    <hr />
+
     <form class="js-tz2utc">
       <h3>Relative TimeZone to Absolute UTC:</h3>
       <pre><code>XTZ.toUTC("<span class="js-dtx-tz">YYYY-03-14 03:15:69.000</span>", "<span class="js-tzx-tz">UTC</span>")
@@ -182,6 +194,7 @@ Asia/Kolkata        +0530 (No DST) (30-min)</pre
       >github.com/therootcompany/tz.js</a
     >
     <script src="./xtz.js"></script>
+    <script src="./tolocalisostring.js"></script>
     <script>
       function $(sel, el) {
         return (el || document.body).querySelector(sel);
@@ -222,6 +235,8 @@ Asia/Kolkata        +0530 (No DST) (30-min)</pre
         $(".js-my-dt-xtz").value = translate(curDt, inTz, outTz).toISOString();
       }
 
+      $(".js-my-dt-local").value = XTZ.toLocalISOString();
+
       var myTz = new Intl.DateTimeFormat("default", {}).resolvedOptions()
         .timeZone;
       $(".js-my-tz").innerText = myTz;

tolocalisostring.js

@@ -0,0 +1,50 @@
+(function (exports) {
+  "use strict";
+
+  // See <https://github.com/coolaj86/AJScript/issues/27>
+
+  function toLocalISOString(dateOrStr) {
+    var d;
+    if (dateOrStr) {
+      d = new Date(dateOrStr);
+    } else {
+      d = new Date();
+    }
+
+    var YYYY = d.getFullYear();
+    var MM = p2(d.getMonth() + 1);
+    var DD = p2(d.getDate());
+    var hh = p2(d.getHours());
+    var mm = p2(d.getMinutes());
+    var ss = p2(d.getSeconds());
+    var sss = d.getMilliseconds().toString().padStart(3, "0");
+
+    var offset = formatOffset(-d.getTimezoneOffset());
+
+    return `${YYYY}-${MM}-${DD}T${hh}:${mm}:${ss}.${sss}${offset}`;
+  }
+
+  function formatOffset(minutes) {
+    if (!minutes) {
+      return "Z";
+    }
+
+    var h = Math.floor(Math.abs(minutes) / 60);
+    var m = Math.abs(minutes) % 60;
+    var offset = "";
+    if (minutes > 0) {
+      offset = "+";
+    } else if (minutes < 0) {
+      offset = "-";
+    }
+
+    // +0500, -0730
+    return offset + p2(h) + p2(m);
+  }
+
+  function p2(x) {
+    return String(x).padStart(2, "0");
+  }
+
+  exports.toLocalISOString = toLocalISOString;
+})(("undefined" === typeof module && window) || exports);

xtz.js

@@ -98,9 +98,7 @@ var XTZ;
     }
 
     // +0500, -0730
-    return (
-      offset + h.toString().padStart(2, "0") + m.toString().padStart(2, "0")
-    );
+    return offset + p2(h) + p2(m);
   }
 
   function toOffsetISOString(d) {
@@ -155,6 +153,27 @@ var XTZ;
     return toOffsetISOString(whole);
   }
 
+  function toLocalISOString(dateOrStr) {
+    var d;
+    if (dateOrStr) {
+      d = new Date(dateOrStr);
+    } else {
+      d = new Date();
+    }
+
+    var YYYY = d.getFullYear();
+    var MM = p2(d.getMonth() + 1);
+    var DD = p2(d.getDate());
+    var hh = p2(d.getHours());
+    var mm = p2(d.getMinutes());
+    var ss = p2(d.getSeconds());
+    var sss = d.getMilliseconds().toString().padStart(3, "0");
+
+    var offset = formatOffset(-d.getTimezoneOffset());
+
+    return `${YYYY}-${MM}-${DD}T${hh}:${mm}:${ss}.${sss}${offset}`;
+  }
+
   XTZ = {
     // bespoke date =>
     // 2021-11-07T3:15:59-0500
@@ -163,6 +182,9 @@ var XTZ;
     // -240 => -0400
     formatOffset: formatOffset,
 
+    // new Date() => "2021-11-07T03:15:59-0500"
+    toLocalISOString: toLocalISOString,
+
     // [ "2021-11-07T08:15:59Z", "America/New_York" ]
     // => "2021-11-07T03:15:59-0500" // 2021-11-07 03:15:59
     toTimeZone: toTimeZone,