Filters an object returning only properties specified

filter-keys.js

/**
 * Filters an object returning only properties specified
 * 
 * @param  {Object} obj  Source object
 * @param  {Array}  keys List of (strings) properties to keep
 * @return {Object}      Object with only props specified in `keys`
 */
export const filterKeys = (obj, keepKeys, dropKeys) => {
    
    if (typeof obj !== 'object')
        throw new Error('Param `obj` must be an object')
    
    const okeys = Object.keys(obj)
    const keep = keepKeys || okeys
    const drop = dropKeys || []
    
    if (!(keep instanceof Array))
        throw new Error('Param `keepKeys` must be an array')
    
    if (!(drop instanceof Array))
        throw new Error('Param `dropKeys` must be an array')
    
    if (!keep.length && !drop.length)
        throw new Error('Either param `keepKeys` or `dropKeys` must contain more than one key')
    
    return okeys
        .reduce((result, it) => {
            if (!keep.includes(it) || drop.includes(it)) return result
            return [...result, it]
        }, [])
        .reduce((result, it) => ({
            ...result,
            [it]: obj[it]
        }), {})
    
}