filter inputs in javascript

filterinputJS.js

const mkLender = (assignedLender, category) => {
    if (assignedLender) {
        const input = assignedLender.toLowerCase().replace(/ /g, '');
        if (input.startsWith("userid:")) {
            const x = /userid:(\d+)/i.exec(input);
            if (x != null)
                return {
                    assignedUser: {"userId": parseInt(x[1])},
                    category: mkCategory(category)
                };
            else {
                throw new Error(`Malformated UserId, ${possibleAssignedLenderMessage}`);
            }
        }
        else if (assignedLender.toLowerCase() === "autoassign") {
            return {
                assignedUser: assignedLender,
                category: mkCategory(category)
            };
        } else {
            throw new Error(`Invalid associated user ${assignedLender}. ${possibleAssignedLenderMessage}`);
        }
    }
};