Deep Object Diffing

objectdiff.js

function deepDiff(obj1, obj2) {
    function changes(obj1, obj2) {
        let diff = {};
        for (let key in obj1) {
            if (obj2.hasOwnProperty(key)) {
                if (typeof obj1[key] === 'object' && typeof obj2[key] === 'object') {
                    let deepChanges = changes(obj1[key], obj2[key]);
                    if (Object.keys(deepChanges).length > 0) {
                        diff[key] = deepChanges;
                    }
                } else if (obj1[key] !== obj2[key]) {
                    diff[key] = { oldValue: obj1[key], newValue: obj2[key] };
                }
            } else {
                diff[key] = { oldValue: obj1[key], newValue: undefined };
            }
        }
        for (let key in obj2) {
            if (!obj1.hasOwnProperty(key)) {
                diff[key] = { oldValue: undefined, newValue: obj2[key] };
            }
        }
        return diff;
    }

    return changes(obj1, obj2);
}

const lhs = { a: 1, b: 2, c: { d: 3 } };
const rhs = { a: 1, b: 3, c: { d: 4 } };

const differences = deepDiff(lhs, rhs);
console.log(differences);