ZCCADCDEDB567ABAE643E15DCF0974E503Z 从查找中忽略列，如果值为 null

Question

假设我有一个 mongoose model 和一个基于机会的值

const findUser = async (username, email) => {
  let foo = null
 
  if (Math.random() > 0.5) foo = "hi" // `foo` now has a chance of turning from null to "hi"

  UserModel.find({ "username": username, "email": email, "winner": foo === null ? 'EXCLUDE THIS SEARCH VALUE' : foo
}

^ This is some real code, in combination with some pseudo code ^

我可以这样实现：

const findUser = async (username, email) => {
  let foo = null
 
  if (Math.random() > 0.5) foo = "hi" // `foo` now has a chance of turning from null to "hi"

  let result;
  if(foo === null)
    result = await UserModel.find({ "username": username, "email": email });
  else
    result = await UserModel.find({ "username": username, "email": email, "winner": foo });
  // ^^ Now I have to type the same thing all over again..
  // I'm wondering if there is a way to include it conditionally?
}

但这里的问题是我必须再次输入相同的内容，只是为了包含另一个字段。 有没有办法有条件地在搜索中包含一列？

Answer 1

可能有一种更简单/更好的方法来实现这一点，但在这种情况下我会做的是像这样构建一个 object。

const findUser = async (username, email) => {
  let foo = null

  let query = {
   username,
   email
  }
 
  if (Math.random() > 0.5) foo = "hi" // `foo` now has a chance of turning from null to "hi"

  if (foo != null) {
    query.winner = foo;
  }

  UserModel.find(query);
}

本质上，创建一个默认的 object，其中包含您的属性，该属性将始终存在。 然后检查你的 foo 值是否不是 null。 如果不是 null，则将其添加到您的查询中并将该查询 object 传递给查找。

Answer 2

您可以将查询提取到变量中，然后根据foo的值对其进行操作。

const findUser = async (username, email) => {
   let foo = null

   if (Math.random() > 0.5) foo = "hi"

   const query = { username, email }

   if (foo) {
      query.winner = foo
   }

   const result = await UserModel.find(query)
}