Compare nested objects in JavaScript and return keys equality

Question

I have two nested objects obj1 and obj2 and I want to compare them and the recursively return an object that for each nested key has a equality-lik

Answer 1

You could create a merged object which will have keys of both object. Loop through this object and compare the values for both obj1 and obj2 for each key. If the property is an object, recursively compare the properties. This will work for any level of nesting. Since the properties could be missing from either of the objects, default parameter = {} is added.

const obj1={prop1:1,prop2:"foo",prop3:{prop4:2,prop5:"bar"},prop7:{pro8:"only in 1"}},
      obj2={prop1:3,prop2:"foo",prop3:{prop4:2,prop5:"foobar"}, prop6: "only in 2"};
    
const isObject = val => typeof val === 'object' && val // required for "null" comparison

function compare(obj1 = {}, obj2 = {}) {
  const output = {},
        merged = { ...obj1, ...obj2 }; // has properties of both

  for (const key in merged) {
    const value1 = obj1[key],
          value2 = obj2[key];

    if (isObject(value1) || isObject(value2))
      output[key] = compare(value1, value2) // recursively call
    else
      output[key] = value1 === value2
  }
  
  return output;
}

console.log(compare(obj1, obj2))