batchloader/lib/cacheloader.js

BatchLoader is a utility for data fetching layer to reduce requests via batching written in TypeScript. Inspired by Facebook's DataLoader

import { MappedBatchLoader } from './mappedbatchloader';
export class CacheLoader {
    constructor(loader, cache = new Map()) {
        this.loader = loader;
        this.cache = cache;
        this.promiseCache = new Map();
    }
    load(key) {
        const { promiseCache } = this;
        let pv = promiseCache.get(key);
        if (pv) {
            return pv;
        }
        const value = this.cache.get(key);
        pv =
            value === undefined
                ? this.loader.load(key).then((val) => {
                    this.set(key, val);
                    return val;
                })
                : Promise.resolve(value);
        promiseCache.set(key, pv);
        return pv;
    }
    loadMany(keys) {
        return Promise.all(keys.map((key) => this.load(key)));
    }
    mapLoader(mapFn) {
        return new MappedBatchLoader(this, mapFn);
    }
    get(key) {
        let pv = this.promiseCache.get(key);
        if (pv) {
            return pv;
        }
        const v = this.cache.get(key);
        if (v === undefined) {
            return undefined;
        }
        pv = Promise.resolve(v);
        this.promiseCache.set(key, pv);
        return pv;
    }
    set(key, value) {
        this.promiseCache.delete(key);
        this.cache.set(key, value);
    }
    delete(key) {
        const pDeleted = this.promiseCache.delete(key);
        const deleted = this.cache.delete(key);
        return pDeleted || deleted;
    }
    clear() {
        this.promiseCache.clear();
        this.cache.clear();
    }
}
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