SOURCE

var obj = new Proxy({},{
    get: function(target,propKey,receiver) {
        console.log(`getting ${propKey}!`);
        return Reflect.get(target,propKey,receiver);
    },
    set: function(target,propKey,value,receiver) {
        console.log(`setting ${propKey}!`);
        return Reflect.set(target,propKey,value,receiver);
    }
});
// obj.count = 0;
// obj.count++;
// console.log(obj.count);

var arry = [1,2,3];
var obj2 = new Proxy(arry, {
    get: function(target, propKey, receiver) {
        console.log(target);
        console.log(propKey);
        // console.log(receiver);
        // console.log(target, propKey, receiver);
        if(propKey < 0) {
            return target[target.length - 1];
        }
        return target[propKey];
    }
})
console.log(obj2[-1]);

// 封装
function createArray(args) {
    const handle = {
        get: function(target, propKey) {
            if(propKey < 0) {
                return target[target.length - 1];
            }
            return target[propKey];
        }
    }
    return new Proxy(args, handle);
} 
console.log(new createArray([1,2,3])[-1]);