Force JavaScript exception/error when reading an undefined object property?

Question

I\'m an experienced C++/Java programmer working in Javascript for the first time. I\'m using Chrome as the browser.

I\'ve created several Javascript classes with fie

Answer 1

This can be achieved using ES6 proxies:

function disallowUndefinedProperties(obj) {
    const handler = {
        get(target, property) {
            if (property in target) {
                return target[property];
            }

            throw new Error(`Property '${property}' is not defined`);
        }
    };

    return new Proxy(obj, handler);
}

// example
const obj = { key: 'value' };
const noUndefObj = disallowUndefinedProperties(obj);

console.log(noUndefObj.key);
console.log(noUndefObj.undefinedProperty); // throws exception