const watch = (target, callback)=>{
	for(const key in target){
		if(typeof target[key] === 'object'){
			target[key] = watch(target[key], callback)
		}
	}
	return new Proxy(target, { set: callback })
}

const state = watch(
	{
		name: 'matt',
		friend: {
			name: 'bob'
		}
	},
	(target, prop, newValue) => {
		console.log(newValue);
	}
)

//state.name = 'Matthew'
state.friend.name = 'Bilbo'