Node.js将mysql查询结果转换为数组

Question

我一直在慢慢学习node.js，以便更好地在我们当前的操作（mysql）和Xero会计之间集成。

我在mysql中有几个表，每个表都有一个JSON列，与其所在的表同名，分别为["invoices","accounts","items","organisations","receipts","taxRates","users","trackingCategories"]。这不是一个json问题。

发送像""select "+ wewant1[i] + " from "+wewant1[i]"这样的查询基本上是简单的"select invoices from invoices"，并且易于迭代。

我可以获得mysql结果列表，但需要将每个单独的“列表”作为结果数组获取。

我最终希望能够将“select invoices from invoices”的结果引用为节点中的“invoices”数组（invoices[0]，invoices[1]等）。

我试图避免“回调地狱”，但仍然无法使其正常工作...任何提示都非常欢迎！

以下是当前代码：

var mysql = require('mysql');

var con = mysql.createConnection({
  host: "10.0.1.103",
  user: "badayaba",
  password: "yadabuba",
  database: "xeroetc"
});

(async function() {

  let wewant1 = ["invoices", "accounts", "items", "organisations", "receipts", "taxRates", "users", "trackingCategories"];

  function getmydata(sql, result, callback) {
    var query = con.query(sql);
    query.on('result', function(row) {
      callback(null, row);
    });
  };

  for (let i = 0; i < wewant1.length; i++) {
    var sql = "select " + wewant1[i] + " from " + wewant1[i];
    getmydata(sql, wewant1[i], function querydata(err, result) {
      console.log(err || result);
      return result;
    });
  };
  con.end();
})();

---

2018年9月10日22:00 GMT-6 谢谢Steven！ 我认为我通过这个得到了理解：

const XeroClient = require('xero-node').AccountingAPIClient;
const XeroErrors = require('xero-node').XeroError;
var mysql = require('mysql');

const config = {
    appType: "private",
    consumerKey: "_____",
    consumerSecret: "_____",
    privateKeyPath: "../../../ssl/_____.pem"
  };

var con = mysql.createConnection({
    host: "_____",
    user: "_____",
    password: "_____",
    database: "xeroetc"
});


(async function(){

let wewant1 = ["invoices","accounts","items","organisations","receipts","taxRates","users","trackingCategories"];

let xero = new XeroClient(config);

function getmydata(it, callback) {
       var sql = "select "+it+" from "+it;
       con.query(sql, function (err, result, fields) {
        if (err) throw err;
        callback(null,result);
    });
  };
  
  const promises = wewant1.map(it => {
     return new Promise((resolve, reject) => {
       getmydata(it, function querydata(err, result) {
         if (err) {
           reject(err);
         } else {
           resolve(result);
         }
       });
     })
  });

  Promise.all(promises)
  .then(results => {
    //results is a array of the resolved promises
    invoices=results[0];
    accounts=results[1];
    items=results[2];
    organisations=results[3];
    receipts=results[4];
    taxRates=results[5];
    users=results[6];
    trackingCategories=results[7];
    console.log(invoices);
    })
  .catch(err => {})
    .then(() => {
        con.end();
    })
})();

- Jon Quiros SV

Answer 1

将数组映射到Promise，然后使用Promise.all。这也解决了您未明确说明的过早关闭连接问题。

var mysql = require('mysql');

var con = mysql.createConnection({
  host: "10.0.1.103",
  user: "badayaba",
  password: "yadabuba",
  database: "xeroetc"
});




let wewant1 = ["invoices", "accounts", "items", "organisations", "receipts", "taxRates", "users", "trackingCategories"];

function getmydata(sql, result, callback) {
  var query = con.query(sql);
  query.on('result', function(row) {
    callback(null, row);
  });
};

const promises = weweant1.map(it => {
  return new Promise((resolve, reject) => {
    getmydata(sql, it, function querydata(err, result) {
      if (err) {
        reject(err);
      } else {
        resolve(result);
      }
    });
  })
});

Promise.all(promises)
  .then(results => {
    //results is a array of the resolved promises
  })
  .catch(err => {})
  .then(() => {
    // then after catch is a finally block
    con.end();
  })

当然，您也可以使用async/await，摆脱then的嵌套。您还可以将getmydata promisify。但是所有方法都遵循同一个原则：等待一组承诺。

使用async/await

如果getmydata返回了一个promise或被声明为async，则以下代码片段将会正常运行，假设它在一个async函数中。如此简洁...

const promises = weweant1.map(it => getmydata(sql, it))

try {
  const results = await Promise.all(promises)
} catch (e) {
  // handle error
} finally {
  con.end();
}

- Steven Spungin