lesson_5.js

// JS Nuggets: Proxies!

// Syntax: var p = new Proxy(target, handler);

// Example 1

var handler = {
    get (target, key) {
        return key in target ? target[key] : 37;
    }
};

var p = new Proxy({}, handler);
p.a = 1;
p.b = undefined;

console.log(p.a, p.b);
console.log('c' in p, p.c);

// Example 2 
let validator = {
    set: function(obj, prop, value) {
        if (prop === "age") {
            if (typeof value !== "number" || Number.isNaN(value)) {
                console.log("Age must be a number")
            }
            if (value < 0) {
                console.log("Age must be a positive number")
            }
        }

        obj[prop] = value;

        return true;
    }
};

let person = new Proxy({}, validator);
person.age ='young';
console.log(person.age)
person.age = -30;
person.age = 100;
console.log(person.age)