JSON Schema Diff

schema_diff.js

function customDiff(obj1, obj2) {
  const result = {};

  // Helper function to check if a value is considered 'empty'
  function isEmpty(val) {
    return val === null || val === "";
  }

  // Recursive function to find differences
  function findDifferences(lhs, rhs, path = '') {
    const checkedKeys = new Set();

    // Check keys from both objects
    const keys = new Set([...Object.keys(lhs), ...Object.keys(rhs)]);
    keys.forEach(key => {
      const currentPath = path ? `${path}.${key}` : key;
      checkedKeys.add(key);

      // Check for presence in both objects
      if (key in lhs && !(key in rhs)) {
        result[currentPath] = { message: 'Key missing in second object', value: lhs[key] };
        return;
      }
      if (!(key in lhs) && key in rhs) {
        result[currentPath] = { message: 'Key missing in first object', value: rhs[key] };
        return;
      }

      const lhsVal = lhs[key];
      const rhsVal = rhs[key];

      // Check for arrays with different lengths
      if (Array.isArray(lhsVal) && Array.isArray(rhsVal)) {
        if (lhsVal.length !== rhsVal.length) {
          result[currentPath] = { message: 'Array lengths differ', lhsLength: lhsVal.length, rhsLength: rhsVal.length };
        }
        return;
      }

      // Check for empty equivalence
      if (isEmpty(lhsVal) && isEmpty(rhsVal)) {
        return; // Ignore empty equivalence
      }

      // Recurse if both are objects and not arrays
      if (typeof lhsVal === 'object' && lhsVal !== null && typeof rhsVal === 'object' && rhsVal !== null) {
        findDifferences(lhsVal, rhsVal, currentPath);
        return;
      }

      // Finally, check for equality of values
      if (lhsVal !== rhsVal) {
        // Ignoring differences in values
        return;
      }
    });
  }

  findDifferences(obj1, obj2);
  return result;
}

// Example usage
const obj1 = {
  details: {
    info: "test",
    moreInfo: [1, 2, 3]
  }
};

const obj2 = {
  details: {
    info: "test",
    moreInfo: [1, 2, 3, 4]
  }
};

const differences = customDiff(obj1, obj2);
console.log(differences);

How to compare Schema Differeences in JSON?

1. Arrays are compared based on length only, regardless of their contents.
2. Null and empty strings are considered equivalent to each other in any comparison.
3. All other value differences are ignored, focusing solely on structural and presence-related differences.