Node.js/TypeScript中如何对多份同键数值型JSON求和？

Hey there! Since you're new to Node.js and TypeScript, let's walk through how to solve this JSON summation problem—we'll build a recursive function that handles nested objects and arrays, which is perfect for your use case.

Step 1: Define TypeScript Types for JSON Values #

First, let's set up types to represent valid JSON values. This helps TypeScript catch errors and gives us better autocomplete:

type JsonValue = string | number | boolean | null | JsonObject | JsonArray;
interface JsonObject {
  [key: string]: JsonValue;
}
interface JsonArray extends Array<JsonValue> {}

Step 2: Build a Recursive Summation Function #

We need a function that can traverse nested structures (objects and arrays) and sum corresponding numeric values. Here's how to do it:

function sumJson(a: JsonValue, b: JsonValue): JsonValue {
  // Sum numeric values directly
  if (typeof a === 'number' && typeof b === 'number') {
    return a + b;
  }

  // Recursively sum nested objects
  if (typeof a === 'object' && a !== null && typeof b === 'object' && b !== null && !Array.isArray(a) && !Array.isArray(b)) {
    const result: JsonObject = {};
    // Grab all keys (since structures are identical, keys should match)
    const allKeys = new Set([...Object.keys(a as JsonObject), ...Object.keys(b as JsonObject)]);
    
    for (const key of allKeys) {
      result[key] = sumJson((a as JsonObject)[key], (b as JsonObject)[key]);
    }
    return result;
  }

  // Recursively sum arrays (matching index positions)
  if (Array.isArray(a) && Array.isArray(b)) {
    return a.map((item, index) => sumJson(item, b[index]));
  }

  // For non-numeric values (strings, booleans, null), keep the value from the first object
  // (Since structures are identical, these values should be the same across all inputs)
  return a;
}

Step 3: Handle Multiple JSON Objects #

To sum more than two JSONs, we can use Array.reduce() to accumulate the results:

function sumMultipleJsons(...jsons: JsonValue[]): JsonValue {
  if (jsons.length === 0) return {}; // Return empty object if no inputs
  return jsons.reduce((accumulator, current) => sumJson(accumulator, current));
}

Testing with Your Example #

Let's plug in your sample JSONs (I filled in the missing value in json2 with 30 for demonstration):

const json1 = { 
  "201809": 2, 
  "metric": "headcount", 
  "quarter1": 60, 
  "careerLevelsGroups": [{ 
    "201809": 2, 
    "quarter1": 60, 
    "careerLevels": [{ 
      "201809": 2, 
      "careerId": "careerId1", 
      "quarter1": 60, 
    }, { 
      "201809": 2, 
      "careerId": "careerId2", 
      "quarter1": 50, 
    }] 
  }] 
};

const json2 = { 
  "201809": 3, 
  "metric": "headcount", 
  "quarter1": 100, 
  "careerLevelsGroups": [{ 
    "201809": 7, 
    "quarter1": 40, 
    "careerLevels": [{ 
      "201809": 9, 
      "careerId": "careerId1", 
      "quarter1": 30 
    }] 
  }] 
};

// Sum the two JSONs
const summedResult = sumMultipleJsons(json1, json2);
console.log(JSON.stringify(summedResult, null, 2));

Output:

{
  "201809": 5,
  "metric": "headcount",
  "quarter1": 160,
  "careerLevelsGroups": [
    {
      "201809": 9,
      "quarter1": 100,
      "careerLevels": [
        {
          "201809": 11,
          "careerId": "careerId1",
          "quarter1": 90
        },
        {
          "201809": 2,
          "careerId": "careerId2",
          "quarter1": 50
        }
      ]
    }
  ]
}

Notes to Keep in Mind #

• Structure Consistency: This solution assumes all input JSONs have identical structures. If there's a mismatch (e.g., a key exists in one but not the other, or different types), you might want to add error handling (like throwing an error or logging a warning).
• Non-Numeric Values: We keep non-numeric values from the first JSON. If you need to validate that these values are identical across all inputs, you can add a check in the function.

内容的提问来源于stack exchange，提问作者user3205921