You misunderstand. Object.assign is as available today as is `typeof foo.bar === 'undefined'` or `_.defaults(...)`. Yet I doubt even the majority of modern code

You misunderstand. Object.assign is as available today as is `typeof foo.bar === 'undefined'` or `_.defaults(...)`. Yet I doubt even the majority of modern code always uses them consistently because `if (foo.bar)` or `foo.bar = foo.bar || 1234` is much simpler and much faster.