promise与async 数据库查询封装对比

• async await

const Config = require("./config");

const MongoClient = require("mongodb").MongoClient;

const client = new MongoClient(Config.dbUrl, { useUnifiedTopology: true });

class Db {
  constructor() {
    // this.connect();
  }
  async connect() {
    try {
      await client.connect();
      return client.db(Config.dbName);
    } catch (e) {
      throw new Error(e);
    }
  }
  async find(collectionName, json) {
    try {
      const db = await this.connect();
      const collection = db.collection(collectionName);
      const docs = await collection.find(json).toArray();
      return docs;
    } catch (e) {
      throw new Error(e);
    }
  }
}

const db = new Db();

(async () => {
  try {
    const docs = await db.find("student", {});
    console.log(docs);
  } catch (e) {
    console.log(e.message);
  }
})();

• promise

const Config = require("./config");

const MongoClient = require("mongodb").MongoClient;

const client = new MongoClient(Config.dbUrl, { useUnifiedTopology: true });

class Db {
  constructor() {
    // this.connect();
  }
  connect() {
    return new Promise((resolve, reject) => {
      client.connect(err => {
        if (err) {
          reject(err);
        } else {
          const db = client.db(Config.dbName);
          resolve(db);
        }
      });
    });
  }
  find(collectionName, json) {
    return new Promise((resolve, reject) => {
      this.connect()
        .then(db => {
          const collection = db.collection(collectionName);
          collection.find(json).toArray((err, docs) => {
            if (err) {
              reject(err);
            } else {
              resolve(docs);
            }
          });
        })
        .catch(e => {
          reject(e)
        });
    });
  }
}

const db = new Db();

db.find("student", {})
  .then(docs => {
    console.log(docs);
  })
  .catch(e => {
    console.log(e.message);
  });