A search function to use with Dexie.js to search an IndexedDB table using an object of where clauses

search.js

let search = function(db, tableName, query) {
    let table = db.table(tableName)

    let clause = Object.keys(query).reduce( (r, n) => {
        if (typeof query[n] === "undefined" || query[n] === null) return r;

        let where = !r ? table.where(n) : r.or(n)

        if (query[n] && query[n].constructor === String) {
            return where.startsWith(query[n])
        }

        return where.equals(query[n])
    }, null)

    return clause
}