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: (target, prop, newValue) => {
				target[prop] = newValue
				callback()
			}
		}
	)
}

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

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