PriorityQueue Implementation in Javascript

class PriorityQueue {
    constructor() {
        this.heap = [];
    }

    insert(value, priority) {
        this.heap.push({ value, priority });
        this.bubbleUp();
    }

    extractMin() {
        if (this.isEmpty()) return null;
        if (this.heap.length === 1) return this.heap.pop().value;

        const min = this.heap[0].value;
        this.heap[0] = this.heap.pop();
        this.bubbleDown();
        return min;
    }

    peek() {
        if (this.isEmpty()) return null;
        return this.heap[0].value;
    }

    isEmpty() {
        return this.heap.length === 0;
    }

    bubbleUp() {
        let index = this.heap.length - 1;
        while (index > 0) {
            let parentIndex = Math.floor((index - 1) / 2);
            if (this.heap[index].priority < this.heap[parentIndex].priority) {
                [this.heap[index], this.heap[parentIndex]] = [this.heap[parentIndex], this.heap[index]];
                index = parentIndex;
            } else {
                break;
            }
        }
    }

    bubbleDown() {
        let index = 0;
        const lastIndex = this.heap.length - 1;
        while (true) {
            let leftChildIndex = 2 * index + 1;
            let rightChildIndex = 2 * index + 2;
            let smallestChildIndex = index;

            if (leftChildIndex <= lastIndex && this.heap[leftChildIndex].priority < this.heap[smallestChildIndex].priority) {
                smallestChildIndex = leftChildIndex;
            }
            if (rightChildIndex <= lastIndex && this.heap[rightChildIndex].priority < this.heap[smallestChildIndex].priority) {
                smallestChildIndex = rightChildIndex;
            }

            if (smallestChildIndex !== index) {
                [this.heap[index], this.heap[smallestChildIndex]] = [this.heap[smallestChildIndex], this.heap[index]];
                index = smallestChildIndex;
            } else {
                break;
            }
        }
    }
}