【Javascript】jsondiffpatch检测到子节点改变了，父节点会标记为改变吗？

答案是：No

但是你也有办法检查哪些父节点受到改变的影响，具体分析如下：

jsondiffpatch is designed to be very granular and identifies changes at the most specific path possible.

If a sub-node changes, the parent node itself is not explicitly identified as "changed" in the jsondiffpatch delta. The delta will only show the specific change at the path of the sub-node.

Why?

jsondiffpatch aims for minimal, atomic changes. It doesn't generate a "cascading" change report up the object tree. It pinpoints the exact property or array element that was added, removed, or modified.

Example

Let's illustrate this with an example:

const jsondiffpatch = require('jsondiffpatch').create();

const originalJson = {
  "id": 1,
  "name": "Product A",
  "details": {
    "price": 100,
    "currency": "USD",
    "dimensions": {
      "width": 10,
      "height": 20
      // "depth": 5 // uncomment to see another type of change
    }
  },
  "tags": ["electronics", "gadget"]
};

const modifiedJson = {
  "id": 1,
  "name": "Product A",
  "details": {
    "price": 100,
    "currency": "USD",
    "dimensions": {
      "width": 12, // <--- This sub-node changed
      "height": 20
    }
  },
  "tags": ["electronics", "gadget"]
};

const delta = jsondiffpatch.diff(originalJson, modifiedJson);

console.log("Original JSON:\n", JSON.stringify(originalJson, null, 2));
console.log("\nModified JSON:\n", JSON.stringify(modifiedJson, null, 2));
console.log("\nDelta (changes):\n", JSON.stringify(delta, null, 2));

// --- Let's also check if 'details' or 'dimensions' objects are marked as direct changes ---
// (They won't be)
const detailsDelta = delta && delta.details;
const dimensionsDelta = detailsDelta && detailsDelta.dimensions;

console.log("\nIs 'details' itself in the delta (as a modified object)?", !!detailsDelta && Object.keys(detailsDelta).length > 0);
console.log("Is 'dimensions' itself in the delta (as a modified object)?", !!dimensionsDelta && Object.keys(dimensionsDelta).length > 0);

if (delta) {
  // To check if a specific parent was "affected", you'd look for its properties in the delta.
  const detailsAffected = 'details' in delta;
  const dimensionsAffected = 'details' in delta && 'dimensions' in delta.details;
  const widthAffected = 'details' in delta && 'dimensions' in delta.details && 'width' in delta.details.dimensions;

  console.log("\nProgrammatic check:");
  console.log("'details' node path is present in delta:", detailsAffected);
  console.log("'dimensions' node path is present in delta:", dimensionsAffected);
  console.log("'width' node path is present in delta:", widthAffected);
}

Output Explanation:

Original JSON:
 {
  "id": 1,
  "name": "Product A",
  "details": {
    "price": 100,
    "currency": "USD",
    "dimensions": {
      "width": 10,
      "height": 20
    }
  },
  "tags": [
    "electronics",
    "gadget"
  ]
}

Modified JSON:
 {
  "id": 1,
  "name": "Product A",
  "details": {
    "price": 100,
    "currency": "USD",
    "dimensions": {
      "width": 12,
      "height": 20
    }
  },
  "tags": [
    "electronics",
    "gadget"
  ]
}

Delta (changes):
 {
  "details": {
    "dimensions": {
      "width": [
        10,
        12
      ]
    }
  }
}

Is 'details' itself in the delta (as a modified object)? true
Is 'dimensions' itself in the delta (as a modified object)? true

Programmatic check:
'details' node path is present in delta: true
'dimensions' node path is present in delta: true
'width' node path is present in delta: true

As you can see from the Delta (changes) output:

1. The delta object has a details property.
2. Inside details, it has a dimensions property.
3. Inside dimensions, it has a width property, which shows the actual change [10, 12].

jsondiffpatch doesn't report details as being replaced by a new details object, nor dimensions as being replaced. It just shows that something inside details.dimensions.width changed.

How to interpret "parent affected":

While the parent itself isn't marked as replaced, its path is present in the delta object if any of its children (or children's children, etc.) have changed.

So, if you want to know if details was "affected," you would check if delta.details exists and has any properties (indicating changes within it). If delta.details.dimensions exists, then dimensions was affected. If delta.details.dimensions.width exists and contains a change array, then width itself changed.