使用Play Scala合并嵌套JSON：按指定规则合并对象

Hey there! Great question. Unfortunately, JavaScript doesn’t have a built-in method that directly handles this specific merge scenario—where you match objects by a specific key (c in your case) and sum the values of another property (d). But creating a custom function to do this is straightforward, and I’ll show you how to implement it step by step.

Approach #

The core idea is:

1. Collect all objects from both arrays, grouping them by the c key.
2. For each group, sum up the d values of all objects in that group.
3. Convert the grouped data back into the array structure you need, then nest it back into the original object hierarchy.

Custom Implementation #

First, let’s build a reusable function that handles the array merging and summing:

function mergeByKeyAndSum(arr1, arr2, matchKey, sumKey) {
  // Use a Map to track cumulative sums for each matchKey value
  const valueMap = new Map();

  // Process the first array
  arr1.forEach(item => {
    const key = item[matchKey];
    valueMap.set(key, (valueMap.get(key) || 0) + item[sumKey]);
  });

  // Process the second array
  arr2.forEach(item => {
    const key = item[matchKey];
    valueMap.set(key, (valueMap.get(key) || 0) + item[sumKey]);
  });

  // Convert the Map back to an array of objects in your desired format
  return Array.from(valueMap.entries()).map(([key, total]) => ({
    [matchKey]: key,
    [sumKey]: total
  }));
}

Example 1: Matching Keys in Both Arrays #

Let’s test this with your first set of JSON objects:

const json1 = {a: {b: [{c: "x" , d: 1}, {c: "y" , d: 2}]} };
const json2 = {a: {b: [{c: "x" , d: 3}, {c: "y" , d: 4}]} };

const mergedResult = {
  a: {
    b: mergeByKeyAndSum(json1.a.b, json2.a.b, 'c', 'd')
  }
};

console.log(mergedResult);
// Output: { a: { b: [ { c: 'x', d: 4 }, { c: 'y', d: 6 } ] } }

Example 2: Partial Matching with New Keys #

Now let’s use your second scenario where json2 has a mix of existing and new keys:

const json2v2 = {a: {b: [{c: "y" , d: 3}, {c: "z" , d: 4}]} };

const mergedResult2 = {
  a: {
    b: mergeByKeyAndSum(json1.a.b, json2v2.a.b, 'c', 'd')
  }
};

console.log(mergedResult2);
// Output: { a: { b: [ { c: 'x', d: 1 }, { c: 'y', d: 5 }, { c: 'z', d: 4 } ] } }

Notes #

• This function is flexible: you can reuse it for different key names (just pass different matchKey and sumKey arguments).
• If your JSON structure has deeper nesting, you can extend this logic with recursion to handle multiple levels, but for the structure you provided, this implementation works perfectly.

内容的提问来源于stack exchange，提问作者Monika