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[dmitry-bym]

The BottomSheet implementation is detailed and functional, but several optimizations can improve performance, maintainability, and clarity. Below are areas for optimization:

1. Event Listener Management
   Current State: Event listeners are added and removed multiple times, especially in initializeSheet, reinitialize, and removeListeners.
   Optimization: Use delegation where possible to minimize adding/removing listeners. For example, a single listener on the sheet can delegate drag handling to specific elements.
   javascript
   Копировать код
   this._sheet.addEventListener("mousedown", (event) => {
   if (event.target.matches("[data-bs-header], [data-bs-footer]")) {
   this.onDragStartMouse(event);
   } else if (event.target.matches("[data-bs-contents]")) {
   this.onDragStartMouseContent(event);
   }
   });
2. Redundant Attribute Updates
   Current State: Attributes like data-bs-scroll and aria-hidden are updated in multiple places.
   Optimization: Create utility functions to set these attributes only if their values change.
   javascript
   Копировать код
   updateAttribute(element, attribute, value) {
   if (element.getAttribute(attribute) !== value) {
   element.setAttribute(attribute, value);
   }
   }

// Usage
updateAttribute(this._sheet, "data-bs-scroll", this._inDrag ? "" : null);
3. Drag Handling Calculations
Current State: Dragging logic involves frequent style updates in updateStyle and relies on requestAnimationFrame.
Optimization:
Use CSS transitions for smoother height updates, avoiding manual frame-based adjustments where possible.
Debounce or throttle frequent calls to updateStyle during dragging to improve performance.
4. Stop Position Handling
Current State: Stops are recalculated with reduce in getClosestStop every time the method is called.
Optimization: Pre-sort and store stops, enabling binary search for faster lookup, especially with larger stop arrays.
javascript
Копировать код
getClosestStop(goal) {
// Assuming stops are pre-sorted
let low = 0, high = this._stops.length - 1;
while (low < high) {
const mid = Math.floor((low + high) / 2);
if (this._stops[mid] < goal) low = mid + 1;
else high = mid;
}
return this._stops[low];
}
5. MutationObserver Optimization
Current State: Mutation observer reinitializes the sheet for any DOM change within the observed subtree.
Optimization: Use filtering in the callback to handle only relevant changes (e.g., child additions/removals affecting data-bs-*).
6. Passive Mode Behavior
Current State: Dragging is disabled in passive mode, but event listeners like mousemove and touchmove still run.
Optimization: Prevent adding drag-related listeners entirely when passive is enabled to avoid unnecessary computation.
7. CSS-Driven Height Adjustments
Current State: JavaScript manually adjusts the style.height of the sheet.
Optimization: Use CSS variables to manage height and transitions. JavaScript can update the CSS variable, leaving the browser to handle rendering.
css
Копировать код
:root {
--sheet-height: 0vh;
}

[data-bs-contents] {
height: var(--sheet-height);
transition: height 0.3s ease-in-out;
}
In JavaScript:

javascript
Копировать код
this._sheet.style.setProperty("--sheet-height", ${this._height}vh);
8. Single Responsibility and Modularity
Current State: Methods like initializeSheet, reinitialize, and setupInitData mix responsibilities.
Optimization: Split responsibilities into smaller, more focused methods. For example, separate the logic for event binding, DOM querying, and state initialization.
9. General Cleanup
Use Constants: Replace hardcoded strings like "[data-bs-overlay]" or "data-bs-scroll" with constants for easier management and debugging.
Avoid Unnecessary DOM Queries: Cache frequently accessed elements (e.g., this._contents, this._overlay) to avoid repeated lookups.
Summary of Benefits
Improved Performance: Throttling, CSS-based transitions, and optimized calculations reduce runtime overhead.
Better Maintainability: Modular, reusable methods and constants simplify debugging and future enhancements.
Enhanced User Experience: CSS transitions and smoother animations create a more responsive interface.
Would you like me to apply these optimizations directly to your code?