Pagerank implemented in plain JS and with graphology.js

pagerank-graphology.js

import Graph from "graphology";

const defaultDampening = 0.85;
const defaultIterations = 40
// graph, or page map: the pages that exist, and that each page links to

/**
 * 
 * @param {Graph} graph
 * @param {number} iterations 
 * @param {number} dampening 
 * @param {*} initialScores 
 * @returns scores
 */
export function pageRank (graph, iterations, dampening, initialScores) {
    // dampening factor - how likely the user is to continue clicking
    dampening = dampening ?? defaultDampening
    iterations = iterations ?? defaultIterations

    let scores = {}

    // set the initial score of each page
    if (initialScores) {
        graph.nodes().forEach((node) => {
            scores[node] = initialScores[node] ?? 1.0;
        })
    } else {
        graph.nodes().forEach((node) => {
            scores[node] = 1.0;
        })
    }

    let i = iterations;

    while (i >= 0) {
        // We want to calculate in stages, so store the new values until all values have been calculated
        let iterationScores = {}
        // Calculate the new score for each page according to the pagerank formula
        graph.nodes().forEach((node) => {
            let score = 1 - dampening
            graph.inboundEdges(node).forEach((edge) => {
                let neighbor = graph.source(edge)
                let count = graph.outEdges(neighbor).length
                let edgeScore = scores[neighbor] / count
                score = score + dampening * edgeScore
            })
            iterationScores[node] = score
        })
        // update the stored final values and continue the loop
        scores = iterationScores
        i = i - 1;
    }
    return scores
}

pagerank.js

const defaultDampening = 0.85;
const defaultIterations = 40
// graph, or page map: the pages that exist, and that each page links to


export function pageRank (graph, iterations, dampening, initialScores) {
    // dampening factor - how likely the user is to continue clicking
    dampening = dampening ?? defaultDampening
    iterations = iterations ?? defaultIterations

    let scores = {}

    // set the initial score of each page
    for (let node in graph) {
        scores[node] = initialScores[node] || 1.0;
    }

    // invert the graph. eg. page a is linked to by pages e and f
    let invertedGraph = {}
    for (let node in graph) {
        invertedGraph[node] = [];
    }

    for (let node in graph) {
        graph[node].forEach((edge) => {
            invertedGraph[edge].push(node)
        })
    }

    let i = iterations;

    while (i >= 0) {
        // We want to calculate in stages, so store the new values until all values have been calculated
        let iterationScores = {}
        // Calculate the new score for each page according to the pagerank formula
        for (let node in graph) {
            let score = 1 - dampening
            invertedGraph[node].forEach((edge) => {
                let count = graph[edge].length
                let edgeScore = scores[edge] / count
                score = score + dampening * edgeScore
            })
            iterationScores[node] = score
        }
        // update the stored final values and continue the loop
        scores = iterationScores
        i = i - 1;
    }
    return scores
}