index.js

let zipTree = null;
function getByZipCode(_zip) {
    // Cast to string
    let zip = String(_zip);
    // Validate
    // - Check zip length
    if (zip.length < 5) {
        zip = "00000".substr(zip.length) + zip;
    } else if (zip.length > 5) {
        return null;
    }
    // - Reject non-numeric
    if (zip.match(/\D/)) {
        return null;
    }
    // Load data if not loaded
    if (zipTree === null) {
        zipTree = require("./data/zip-tree.json");
    }
    const p = zip.split("").map(x => parseInt(x, 10));
    const place =
        zipTree[p[0]] &&
        zipTree[p[0]][p[1]] &&
        zipTree[p[0]][p[1]][p[2]] &&
        zipTree[p[0]][p[1]][p[2]][p[3]] &&
        zipTree[p[0]][p[1]][p[2]][p[3]][p[4]]
            ? zipTree[p[0]][p[1]][p[2]][p[3]][p[4]]
            : null;
    // Octal check
    if (place === null && typeof _zip !== "string" && _zip < 0o7777) {
        return getByZipCode(_zip.toString(8));
    }
    return place;
}

let locTree = null;
function distance(lat, long, op) {
    return Math.sqrt(Math.pow(lat - op.lat, 2) + Math.pow(long - op.long, 2));
}
function getByLocation(lat, long, count) {
    // Validate
    if (
        typeof lat === "undefined" ||
        isNaN(parseInt(lat, 10)) ||
        typeof long === "undefined" ||
        isNaN(parseInt(long, 10))
    ) {
        return null;
    }
    if (locTree === null) {
        locTree = require("./data/loc-tree.json");
    }
    const latIndex = Math.round(Math.abs(parseFloat(lat, 10)));
    const longIndex = Math.round(Math.abs(parseFloat(long, 10)));
    if (!locTree.zones[latIndex] || !locTree.zones[latIndex][longIndex]) {
        return null;
    }
    const zone = locTree.zones[latIndex][longIndex];
    // Return 1
    if (!count || count === 1) {
        let d = distance(lat, long, locTree.index[zone[0]]);
        let index = 0;
        for (let i = 1; i < zone.length; i += 1) {
            const nd = distance(lat, long, locTree.index[zone[i]]);
            if (nd < d) {
                d = nd;
                index = i;
            }
        }
        return locTree.index[zone[index]];
    }
    // Return multiple
    const sortzone = zone.map(index => {
        const place = locTree.index[index];
        place.distance = distance(lat, long, place);
        return place;
    });
    return sortzone.sort((a, b) => a.distance - b.distance).slice(0, count);
}

module.exports = {
    getByLocation,
    getByZipCode,
};