在mongodb中添加文档值

Question

我正在尝试查找对象中值的平均值。这些值保存在mongodb中，但保存为字符串。我想找到平均值并返回表格。

文档：

{
{
  "_id": "someId",
  "english": "78",
  "literature": "78",
  "period": "1st Period"
}{
  "_id": "someId",
  "english": "90",
  "literature": "90",
  "period": "2nd Period"
}{
  "_id": "someId",
  "english": "70",
  "literature": "99",
  "period": "3rd Period"
}{
  "_id": "someId",
  "english": "50",
  "literature": "60",
  "period": "First Sem. Exam"
}{
  "_id": "someId",
  "english": "68",
  "literature": "88",
  "period": "4th Period"
}{
  "_id": "someId",
  "Average": "",
  "period": "First Sem. Average"
}{
  "_id": "someId",
  "english": "40",
  "literature": "77",
  "period": "5th Period"
}{
  "_id": "someId",
  "english": "70",
  "literature": "66",
  "period": "6th Period"
}{
  "_id": "someId",
  "english": "55",
  "literature": "79",
  "period": "Second Sem. Exam"
}{
  "_id": "someId",
  "Average": "",
  "period": "Second Sem. Average"
}
}

如文档中所述，我想获取1st Period, 2nd Period, 3rd Period和First Sem. Exam的平均值并将其返回到表中

有没有办法实现这一目标？

Answer 1

请记住，docs是一个数组，这应该给您一个很好的主意，如何获得英语平均水平。首先，从数组中提取所需的四个周期。然后，您提取所需的结果。最后，您只需要进行平均即可。

const filteredDocs = docs.filter(element => {
    return (
        element.period === "1st Period" ||
        element.period === "2nd Period" ||
        element.period === "3rd Period" ||
        element.period === "First Sem. Exam"
    );
});

const englishResults = filteredDocs.map(element => {
    return parseInt(element.english);
});

const englishAverage =
    englishResults.reduce((a, b) => a + b, 0) / englishResults.length;