Shadowing Dictionary

Shadow.js

function Shadow() {
    return new Proxy({}, {
        get: function (target, name) {
            if (name in target) {
                let stack = target[name];
                return stack[stack.length - 1];
            } else {
                return undefined;
            }
        },
        has: function (target, name) {
            return (name in target);
        },
        set: function (target, name, value) {
            if (name in target) {
                target[name].push(value);
            } else {
                target[name] = [value];
            }
            return true;
        },
        deleteProperty: function (target, name) {
            if (!(name in target)) {
                return false;
            }
            if (target[name].length > 1) {
                target[name].pop();
            } else {
                delete target[name];
            }
            return true;
        }
    })
}