javascript - Nodejs迭代后读取数组

Question

我是 Nodejs 和异步语言的新手。我正在尝试从 sqlite3 读取数据并将它们推送到数组中。最后打印数组。我已成功将数据推送到数组，并且可以从迭代内部记录它们。但是当我尝试从外部读取数组时，数组看起来像是空的。

var express = require('express');
var app = express();

var sqlite3 = require('sqlite3').verbose();
var db = new sqlite3.Database('testDb');

app.use(express.static(__dirname + '/public'));

db.serialize(function() {
  var infoCOllection = [];

  db.each("SELECT rowid AS id, info FROM lorem", function(err, row) {

    infoCOllection.push(row.id + ": " + row.info);
  });
        console.log(infoCOllection);
  });

db.close();

app.listen(3000);
console.log('sever is run on port 3000');

我阅读了很多关于回调和nodejs的示例和解释，但不理解其结构及其与我的代码的关系。任何人都可以帮助我解决我的代码问题。提前致谢

Answer 1

来自docs

Database#each(sql, [param, ...], [callback], [complete])

完成db.each后可以得到array，如下所示

db.each("SELECT rowid AS id, info FROM lorem", function(err, row) {
    infoCOllection.push(row.id + ": " + row.info);
}, function(err, rows){ //callback for completion of .each method
      console.log(infoCOllection); //you can have your array printed here
});