rack-node/lib/similarity/CosineSimilarity.js

write like human, search like computer

"use strict";
/**
 * Parvez M Robin
 * this@parvezmrobin.com
 * Jul 07, 2020
 */
Object.defineProperty(exports, "__esModule", { value: true });
class CosineSimilarity {
    constructor(listA, listB) {
        this.listA = listA;
        this.listB = listB;
    }
    getScore() {
        const listAItemOccurrenceCount = new Map();
        for (const item1 of this.listA) {
            if (item1) {
                listAItemOccurrenceCount.set(item1, (listAItemOccurrenceCount.get(item1) || 0) + 1);
            }
        }
        const listBItemOccurrenceCount = new Map();
        for (const item2 of this.listB) {
            if (item2) {
                listBItemOccurrenceCount.set(item2, (listBItemOccurrenceCount.get(item2) || 0) + 1);
            }
        }
        const listAValues = [...listAItemOccurrenceCount.values()];
        const l2NormA = listAValues
            .map(x => x * x)
            .reduce((sum, x) => x + sum) ** 0.5;
        const listBValues = [...listBItemOccurrenceCount.values()];
        const l2NormB = listBValues
            .map(x => x * x)
            .reduce((sum, x) => x + sum) ** 0.5;
        let aDotB = 0;
        for (const token of listAItemOccurrenceCount.keys()) {
            if (!listBItemOccurrenceCount.has(token)) {
                continue;
            }
            aDotB += listAItemOccurrenceCount.get(token) * listBItemOccurrenceCount.get(token);
        }
        const cosineRatio = aDotB / ((l2NormA * l2NormB) + Number.EPSILON);
        return cosineRatio;
    }
}
exports.default = CosineSimilarity;