我在验证和向数据库中插入多个条目时遇到问题。
nodejs查询在for循环中，但查询方法是异步执行的。并非参数“snapshot”中的所有条目都插入到数据库中。我怎样才能解决这个问题？
这里我设计了一个流程图来向你展示我的逻辑。

我非常感谢你的帮助。
提前谢谢。
这是我的密码：

function setAddListener(userId, snapshot) {

  //var item = snapshot.val();

  //var key = Object.keys(snapshot.val())[0];
  //var size = Object.keys(snapshot.val()).length;

  for (var i = 0; i < Object.keys(snapshot.val()).length; i++) {
    var item = Object.values(snapshot.val())[i];
    //console.log(item);
    console.log(item.shoppingListName);
    console.log(item.userId);
    console.log(item.shoppingListsKey);
    console.log(item.shoppingListKey);

    console.log("QUERY: " + "SELECT * FROM bc_shopping_list WHERE shopping_list_id = '" + item.shoppingListKey + "'");

    databasemysql.query("SELECT * FROM bc_shopping_list WHERE shopping_list_id = '" + item.shoppingListKey + "'").then(rows => {
      //console.log(results.length);
      if (error) throw error;

      if (results.length == 1) {
        console.log("Shopping-List exists :" + item.shoppingListName);
      } else {
        console.log("Not exits");

        //console.log("INSERT INTO `bc_shopping_list`(`shopping_list_id`, `user_id_fk`, `article_user_id_fk`, `shopping_list_picture_id`, `article_search`, `shopping_list_name`, `shopping_list_quantity`, `unit_id_fk`, `shopping_list_durability`, `shopping_list_bought`, `place_id_fk`, `firebase_id`) VALUES ('" + item.shoppingListKey + "', '" + item.userId + "', " + item.articleId + ", '', NULL,'" + item.shoppingListName + "', " + item.shoppingListQuantity + ", " + item.unitId+1 + ", '" + item.shoppingListDurability + "', " + item.shoppingListBought + ", " + item.placeId + ", '" + item.shoppingListsKey);

        //connection.query("INSERT INTO `bc_shopping_list`(`shopping_lists_name`, `user_id_fk`, `shopping_lists_bought`, `firebase_id`) VALUES ('" + dataSnapshot.val().shoppingListsName + "','" + dataSnapshot.val().userId + "', " + dataSnapshot.val().shoppingListsBought + ", '" +  postId2 + "')", function (error, results, fields) {                                                                                                                                                                                                                                                               
        //console.log("INSERT INTO `bc_shopping_list`(`shopping_list_id`, `user_id_fk`, `article_user_id_fk`, `shopping_list_picture_id`, `article_search`, `shopping_list_name`, `shopping_list_quantity`, `unit_id_fk`, `shopping_list_durability`, `shopping_list_bought`, `place_id_fk`, `firebase_id`) VALUES ('" + item.shoppingListKey + "', '" + item.userId + "', " + item.articleId + ", '', NULL,'" + item.shoppingListName + "', " + item.shoppingListQuantity + ", " + item.unitId+1 + ", '" + item.shoppingListDurability + "', " + item.shoppingListBought + ", " + item.placeId + ", '" + item.shoppingListsKey + "')");
        connection.query("INSERT INTO `bc_shopping_list`(`shopping_list_id`, `user_id_fk`, `article_user_id_fk`, `shopping_list_picture_id`, `article_search`, `shopping_list_name`, `shopping_list_quantity`, `unit_id_fk`, `shopping_list_durability`, `shopping_list_bought`, `place_id_fk`, `firebase_id`) VALUES ('" + item.shoppingListKey + "', '" + item.userId + "', " + item.articleId + ", '', NULL,'" + item.shoppingListName + "', " + item.shoppingListQuantity + ", " + item.unitId + 1 + ", '" + item.shoppingListDurability + "', " + item.shoppingListBought + ", " + item.placeId + ", '" + item.shoppingListsKey + "')", function(error, results, fields) {
          console.log("Shopping-Lists Added :" + item.shoppingListName);
          //console.log("INSERT INTO `bc_shopping_list`(`shopping_list_id`, `user_id_fk`, `article_user_id_fk`, `shopping_list_picture_id`, `article_search`, `shopping_list_name`, `shopping_list_quantity`, `unit_id_fk`, `shopping_list_durability`, `shopping_list_bought`, `place_id_fk`, `firebase_id`) VALUES ('" + item.shoppingListKey + "', '" + item.userId + "', " + item.articleId + ", '', NULL,'" + item.shoppingListName + "', " + item.shoppingListQuantity + ", " + item.unitId+1 + ", '" + item.shoppingListDurability + "', " + item.shoppingListBought + ", " + item.placeId + ", '" + item.shoppingListsKey + "')");
        });
      }
    });
  }
}

2条答案

按热度按时间

f0ofjuux1#

沿着这条线。

function setAddListener(userId, snapshot) {
  const keys = Object.keys(snapshot.val());

  const results = keys.map((item) => {
    return databasemysql.query("SELECT * FROM bc_shopping_list WHERE shopping_list_id = '" + item.shoppingListKey + "'")
  });

  Promise.all(results).then((data) => {
    // data is an array of resolved queries.
    // do your operations here
  });
}

赞(0）回复(0）举报 2021-06-20

j2qf4p5b2#

而不是使用 for loop 使用 map . 在Map内部返回每个查询 .then . 因为 map 返回一个新数组，您将得到一个承诺数组。然后把那个数组传给 Promise.all([yourArray]) . 那样的话你会的 resolve 你所有的疑问。请停止使用 var 一般来说。千万不要用它来做手术 for loop . 这是不鼓励我的谷歌风格的指南。https://google.github.io/styleguide/jsguide.html#features-局部变量声明

nodejs验证和循环中的多个插入

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