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javascript - Node.js mysql 结果到数组

问题描述

我一直在慢慢学习 node.js，以便我可以更好地整合我们当前的许多操作（mysql）和 Xero 会计之间的东西。

我在 mysql 中有几个表，每个表用于 ["invoices","accounts","items","organisations","re​​ceipts","taxRates","users","trackingCategories"] 并且每个表都有一个JSON 列与其所在的表同名。这不是 json 问题。

从 "+wewant1[i]" 发送像 ""select "+ wewant1[i] + " 这样的查询基本上是简单的“从发票中选择发票”并且易于迭代。

我可以将 mysql 结果列出，但需要将每个单独的“列表”作为结果数组。

我最终希望能够将“从发票中选择发票”的结果作为节点中的“发票”数组（发票 [0]、发票 [1] 等）引用。

我已经尝试避免“回调地狱”，但仍然无法让它发挥作用......非常欢迎任何提示！

这是当前代码：

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();
})();

20180910 22:00 GMT-6 感谢史蒂文！我想我明白了：

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();
    })
})();

标签： javascriptmysqljsonnode.jsxero-api

解决方案

将您的数组映射到承诺，然后使用Promise.all. 这也解决了您过早关闭连接的未说明问题。

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();
  })

当然你也可以使用async/await并摆脱then嵌套。您还可以承诺getmydata. 不过，它们都使用相同的原则： 等待一系列承诺。

使用异步/等待

如果getmydata返回一个promiseor 被声明async，下面的代码片段会做，假设它在一个async函数中。干净多了...

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

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

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