Error on reading non-existent property
Usually, an attempt to read a non-existent property returns undefined.
Create a proxy that throws an error for an attempt to read of a non-existent property instead.
That can help to detect programming mistakes early.
Write a function wrap(target) that takes an object target and return a proxy that adds this functionality aspect.
That???s how it should work:
let user = {
name: "John"
};
function wrap(target) {
return new Proxy(target, {
/* your code */
});
}
user = wrap(user);
alert(user.name); // John
alert(user.age); // ReferenceError: Property doesn't exist: "age"let user = {
name: "John"
};
function wrap(target) {
return new Proxy(target, {
get(target, prop, receiver) {
if (prop in target) {
return Reflect.get(target, prop, receiver);
} else {
throw new ReferenceError(`Property doesn't exist: "${prop}"`)
}
}
});
}
user = wrap(user);
alert(user.name); // John
alert(user.age); // ReferenceError: Property doesn't exist: "age"