Dijkstra.js

class Node {
    constructor (value, priority) {
        this.value = value;
        this.priority = priority;
    }
}

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

    enqueue (value, priority) {
        const node = new Node(value, priority);
        this.values.push(node);
        this.bubbleUp();
    }

    bubbleUp () {
        let idx = this.values.length - 1;
        const element = this.values[idx];

        while (idx > 0) {
            const parentIdx = Math.floor((idx - 1) / 2);
            const parent = this.values[parentIdx];
            if (parent.priority <= element.priority) break;
            this.values[parentIdx] = element;
            this.values[idx] = parent;
            idx = parentIdx;
        }
    }

    dequeue () {
        const max = this.values[0];
        const end = this.values.pop();
        if (this.values.length > 0){
            this.values[0] = end;
            this.sinkDown();
        }
        return max;
    }

    sinkDown () {
        let idx = 0;
        const element = this.values[idx];
        const length = this.values.length;
        while (true) {
            const leftChildIdx = 2 * idx + 1;
            const rightChildIdx = 2 * idx + 2;
            let leftChild = null;
            let rightChild = null;
            let swapIdx = null;

            if (leftChildIdx < length) {
                leftChild = this.values[leftChildIdx];
                if (leftChild.priority < element.priority) {
                    swapIdx = leftChildIdx;
                }
            }

            if (rightChildIdx < length) {
                rightChild = this.values[rightChildIdx];
                if (
                    (swapIdx === null && rightChild.priority < element.priority) ||
                    (swapIdx !== null && rightChild.priority < leftChild.priority)
                ) {
                    swapIdx = rightChildIdx;
                }
            }

            if (swapIdx === null) break;

            this.values[idx] = this.values[swapIdx];
            this.values[swapIdx] = element;
            idx = swapIdx;
        }
    }
}

class WeightedGraph {
    constructor () {
        this.adjacencyList = {};
    }

    addVertex (vertex) {
        if (!this.adjacencyList[vertex]) {
            this.adjacencyList[vertex] = [];
        }
    }

    addEdge (vertex1, vertex2, weight) {
        if (this.adjacencyList[vertex1] && this.adjacencyList[vertex2]) {
            this.adjacencyList[vertex1].push({ node: vertex2, weight });
            this.adjacencyList[vertex2].push({ node: vertex1, weight });
        }
    }

    dijkstra (start, end) {
        const queue = new PriorityQueue();
        const distances = {};
        const previous = {};
        let path = [];
        let length = 0;
        let smallest;

        for (const vertex in this.adjacencyList) {
            previous[vertex] = null;
            if (vertex === start) {
                distances[vertex] = 0;
                queue.enqueue(vertex, 0);
            } else {
                distances[vertex] = Infinity;
                queue.enqueue(vertex, Infinity);
            }
        }

        while (queue.values.length) {
            smallest = queue.dequeue().value;
            if (smallest === end) {
                length = distances[smallest];
                while (previous[smallest]) {
                    path.push(smallest);
                    smallest = previous[smallest];
                }
                path.push(start);
                path = path.reverse();
                break;
            }
            if (smallest || distances[smallest] !== Infinity) {
                for (const neighbor of this.adjacencyList[smallest]) {
                    const neighborVertex = neighbor.node;
                    const neighborWeight = neighbor.weight;
                    const newDistance = distances[smallest] + neighborWeight;
                    if (newDistance < distances[neighborVertex]) {
                        distances[neighborVertex] = newDistance;
                        previous[neighborVertex] = smallest;
                        queue.enqueue(neighborVertex, newDistance);
                    }
                }
            }
        }

        return { path, length };
    }
}

const graph = new WeightedGraph();

graph.addVertex('A');
graph.addVertex('B');
graph.addVertex('C');
graph.addVertex('D');
graph.addVertex('E');
graph.addVertex('F');
graph.addEdge('A','B', 4);
graph.addEdge('A','C', 2);
graph.addEdge('B','E', 3);
graph.addEdge('C','D', 2);
graph.addEdge('C','F', 4);
graph.addEdge('D','E', 3);
graph.addEdge('D','F', 1);
graph.addEdge('E','F', 1);

graph.dijkstra('A', 'E');