Deeply merge 2 objects, i.e. deep Object.assign

mergeObjects.js

const mergeObjects = (target, source) =>
{
    const isObject = item => item && typeof item === "object" && !Array.isArray(item) && item !== null

    if(isObject(target) && isObject(source))
    {
        for(let key in source)
        {
            if(source.hasOwnProperty(key) && isObject(source[key]))
            {
                if(!target.hasOwnProperty(key))
                {
                    target[key] = {}
                }

                mergeObjects(target[key], source[key])
            }

            else
            {
                target[key] = source[key]
            }
        }
    }

    return target
}