Simple Angular Object Cache

cache.service.ts

import { Injectable } from '@angular/core';


@Injectable()
export class CacheService {
  _dict: Map<string, CacheItem>;
  constructor() {
    this._dict = new Map<string, CacheItem>();
  }

  public Get(key: string): any {
    if (this.Exists(key)) {
      return this._dict.get(key).Item;
    }
    return undefined;
  }

  public GetOrSetValue<T>(key: string, lookup: () => Promise<T>, expMinutes: number): Promise<T> {
    if (this.Exists(key)) {
      return Promise.resolve(this.Get(key) as T);
    }
    return lookup().then(result => {
        this.Set(key, result, expMinutes);
        return result;
      });
  }

  public Set(key: string, value: any, expMinutes: number) {
    this._dict.set(key, { Item: value, ExpirationTime: (Date.now() + expMinutes * 60000)} as CacheItem);
  }

  public Exists(key: string): boolean {
    if (this._dict.has(key)) {
      const val = this._dict.get(key);
      if (val.ExpirationTime > Date.now()) {
        return true;
      }
      this._dict.delete(key);
    }
    return false;
  }

  public Delete(key: string): boolean {
    return this._dict.delete(key);
  }

  public Clear() {
    this._dict = new Map<string, CacheItem>();
  }

  public ClearCategory(category: string): number {
    let count = 0;
    this._dict.forEach((value: CacheItem, key: string) => {
      if (key.startsWith(category + ':')) {
        if (this._dict.delete(key)) {
          count++;
        }
      }
    });
    return count;
  }
}

class CacheItem {
  public Item: any;
  public ExpirationTime: number;
}