ES6 Proxies Object

proxies.js

const log = console.log

// https://www.youtube.com/watch?v=_5X2aB_mNp4
const Undefined = new Proxy(function() {}, {
	// if call Undefined as function, you will get Undefined
	get(target, key, receiver) {
		return Undefined;
	},
	apply() {
		return Undefined;
	},
})

function seatBelt (obj) {
	return new Proxy(obj, {
		get(target, key) {
			// Check does this property actually exist
			const accessedProperty = Reflect.get(target, key)
			if (typeof accessedProperty === 'object') return seatBelt(accessedProperty)
			else if (accessedProperty == undefined) return Undefined
			return accessedProperty
		},
	})
}


// Example - missing value handler
const handler = {
	get (target, key) { return key in target ? target[key] : 'could not found' }
}

const obj2 = new Proxy({}, handler)
obj.a = 1
obj.b = 2
log(p.a, p.b)
log('c' in p, p.c)

// Example - validater
const validator = {
	set: function(obj, prop, value) {
		if (prop === 'age') {
			if (typeof value !== 'number' || Number.isNaN(value)) {
				console.log('Age must be a number')
				// return error
			}
			if (value <= 0) {
				console.log('Age must be a positive number')
				// return error
			}
			obj[prop] = value
			return true
		}	
	}
}

let person = new Proxy({}, validator)