Review per @ryanhamley

src/ui/hash.js

@@ -89,7 +89,7 @@ class Hash {
                 return part;
             }).filter(a => a);
             if (!found) {
-                parts.push(`${this._hashName || ''}=${hash}`);
+                parts.push(`${this._hashName}=${hash}`);
             }
             return `#${parts.join('&')}`;
         }
@@ -100,6 +100,7 @@ class Hash {
     _getCurrentHash() {
         const hash = window.location.hash.replace('#', '');
         if (this._hashName) {
+            // Split the parameter-styled hash into parts and find the value we need
             const keyval = hash.split('&').map(
                 part => part.split('=')
             ).find(part => part[0] === this._hashName);
@@ -110,7 +111,7 @@ class Hash {
 
     _onHashChange() {
         const loc = this._getCurrentHash();
-        if (loc.length >= 3 && !loc.some(v => isNaN(+v))) {
+        if (loc.length >= 3 && !loc.some(v => isNaN(v))) {
             this._map.jumpTo({
                 center: [+loc[2], +loc[1]],
                 zoom: +loc[0],

src/ui/map.js

@@ -173,7 +173,9 @@ const defaultOptions = {
  *
  * @param {(boolean|string)} [options.hash=false] If `true`, the map's position (zoom, center latitude, center longitude, bearing, and pitch) will be synced with the hash fragment of the page's URL.
  *   For example, `http://path/to/my/page.html#2.59/39.26/53.07/-24.1/60`.
- *   If a string is provided, it will be used as the name for a parameter-styled hash, e.g. `http://path/to/my/page.html#map=2.59/39.26/53.07/-24.1/60&foo=bar`.
+ *   An additional string may optionally be provided to indicate a parameter-styled hash,
+ *   e.g. http://path/to/my/page.html#map=2.59/39.26/53.07/-24.1/60&foo=bar, where foo
+ *   is a custom parameter and bar is an arbitrary hash distinct from the map hash.
  * @param {boolean} [options.interactive=true] If `false`, no mouse, touch, or keyboard listeners will be attached to the map, so it will not respond to interaction.
  * @param {number} [options.bearingSnap=7] The threshold, measured in degrees, that determines when the map's
  *   bearing will snap to north. For example, with a `bearingSnap` of 7, if the user rotates

test/unit/ui/hash.test.js

@@ -67,7 +67,7 @@ test('hash', (t) => {
         t.equal(map.getBearing(), 30);
         t.equal(map.getPitch(), 60);
 
-        window.location.hash = '#4/wronlgy/formed/hash';
+        window.location.hash = '#4/wrongly/formed/hash';
 
         t.false(hash._onHashChange());