Cheap hash for javascript

checksum.js

export default (s)=> {
    let hash = 0
    let strlen = s.length

    if ( strlen === 0 ) {
        return hash;
    }

    for (let i = 0; i < strlen; i++) {
        let c = s.charCodeAt(i)

        hash = ((hash << 5) - hash) + c
        hash = hash & hash
    }

    return hash
}