How to do a deep comparison between 2 objects with lodash?

Question

I have 2 nested objects which are different and I need to know if they have a difference in one of their nested properties.

var a = {}; var b = {};  a.prop1 = 2; a.prop2 = { prop3: 2 };  b.prop1 = 2; b.prop2 = { prop3: 3 }; 

The object could be much more complex with more nested properties. But this one is a good example. I have the option to use recursive functions or something with lodash...

Answer 1

An easy and elegant solution is to use _.isEqual, which performs a deep comparison:

var a = {}; var b = {};  a.prop1 = 2; a.prop2 = { prop3: 2 };  b.prop1 = 2; b.prop2 = { prop3: 3 };  console.log(_.isEqual(a, b)); // returns false if different

<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.4/lodash.min.js"></script>

However, this solution doesn't show which property is different.

Answer 2

If you need to know which properties are different, use reduce():

_.reduce(a, function(result, value, key) {     return _.isEqual(value, b[key]) ?         result : result.concat(key); }, []); // → [ "prop2" ]