#standardSQL
CREATE TEMPORARY FUNCTION geohashEncode(latitude FLOAT64, logitude FLOAT64, precision FLOAT64)
RETURNS STRING
  LANGUAGE js
  AS """
    var Geohash = {};
    /* (Geohash-specific) Base32 map */
    Geohash.base32 = '0123456789bcdefghjkmnpqrstuvwxyz';

    lat = Number(latitude);
    lon = Number(logitude);
    precision = Number(precision);

    if (isNaN(lat) || isNaN(lon) || isNaN(precision)) throw new Error('Invalid geohash');

    var idx = 0; // index into base32 map
    var bit = 0; // each char holds 5 bits
    var evenBit = true;
    var geohash = '';

    var latMin =  -90, latMax =  90;
    var lonMin = -180, lonMax = 180;

    while (geohash.length < precision) {
        if (evenBit) {
            // bisect E-W longitude
            var lonMid = (lonMin + lonMax) / 2;
            if (lon >= lonMid) {
                idx = idx*2 + 1;
                lonMin = lonMid;
            } else {
                idx = idx*2;
                lonMax = lonMid;
            }
        } else {
            // bisect N-S latitude
            var latMid = (latMin + latMax) / 2;
            if (lat >= latMid) {
                idx = idx*2 + 1;
                latMin = latMid;
            } else {
                idx = idx*2;
                latMax = latMid;
            }
        }
        evenBit = !evenBit;

        if (++bit == 5) {
            // 5 bits gives us a character: append it and start over
            geohash += Geohash.base32.charAt(idx);
            bit = 0;
            idx = 0;
        }
    }

    return geohash;
""";

select geohashEncode(38.2842289, -0.5580645, 6);