fix: Prevent duplicate PanelSnap instances on the same container

src/panelSnap.js

@@ -28,9 +28,13 @@ export default class PanelSnap {
     };
 
     this.container = this.options.container;
+    if (this.container.dataset.panelsnapId) {
+      throw new Error('PanelSnap is already initialised on this container, aborting.');
+    }
 
     INSTANCE_COUNTER += 1;
     this.instanceIndex = INSTANCE_COUNTER;
+    this.container.dataset.panelsnapId = this.instanceIndex;
 
     this.scrollingContainer = getScrollingElement(this.container);
     this.panelList = document.querySelectorAll(`[data-panelsnap-id="${this.instanceIndex}"] ${this.options.panelSelector}`);

src/panelSnap.test.js

@@ -5,4 +5,18 @@ describe('Constructor', () => {
     const instance = new PanelSnap();
     expect(instance).toBeInstanceOf(PanelSnap);
   });
+
+  test('prevents duplicate init of panelSnap on the same element', () => {
+    const container = document.createElement('div');
+    // eslint-disable-next-line no-unused-vars
+    const firstInstance = new PanelSnap({ container });
+    expect(() => new PanelSnap({ container })).toThrow('already initialised');
+  });
+
+  test('prevents duplicate init of panelSnap on the same element', () => {
+    const container = document.createElement('div');
+    // eslint-disable-next-line no-unused-vars
+    const firstInstance = new PanelSnap({ container });
+    expect(() => new PanelSnap({ container })).toThrow('already initialised');
+  });
 });