Multiple key names, same pair value

Question

I\'m trying to setup an object literal in a JavaScript script that has a key with multiple names. referring to the same object value i.e. something like these that I have al

Answer 1

Now this may be overkill for you, but here's a generic function that will create an object with "multiple keys." What it actually does is have one real property with the actual value, and then defines getters and setters to forward operations from the virtual keys to the actual property.

function multiKey(keyGroups) {
    let obj = {};
    let props = {};

    for (let keyGroup of keyGroups) {
        let masterKey = keyGroup[0];
        let prop = {
            configurable: true,
            enumerable: false,

            get() {
                return obj[masterKey];
            },

            set(value) {
                obj[masterKey] = value;
            }
        };

        obj[masterKey] = undefined;
        for (let i = 1; i < keyGroup.length; ++i) {
            if (keyGroup.hasOwnProperty(i)) {
                props[keyGroup[i]] = prop;
            }
        }
    }

    return Object.defineProperties(obj, props);
}

This is less sketchy than you would expect, has basically no performance penalty once the object is created, and behaves nicely with enumeration (for...in loops) and membership testing (in operator). Here's some example usage:

let test = multiKey([
    ['north', 'up'],
    ['south', 'down'],
    ['east', 'left'],
    ['west', 'right']
]);

test.north = 42;
test.down = 123;

test.up; // returns 42
test.south; // returns 123

let count = 0;
for (let key in test) {
    count += 1;
}

count === 4; // true; only unique (un-linked) properties are looped over

Taken from my Gist, which you may fork.