Merge two objects (not recursive), but only keep properties that already exist on the target object.

mergeExistingProps.js

const R = require('ramda');

const mergeExistingProps = (target, updater) => {
    const targetClone = R.clone(target);

    for (const prop in targetClone) {
        if (Object.prototype.hasOwnProperty.call(updater, prop)) {
            targetClone[prop] = updater[prop];
        }
    }

    return targetClone;
};

module.exports = mergeExistingProps;

Open to ideas of how to make this recursive but also readable 😆 not sure how to quickly check if updater[prop] should trigger recursion.