Show Google Map Location nearest to you

by Ben Clayton

HTML

<script src="http://maps.google.com/maps/api/js?sensor=false"></script>
<div id="map">postcode entry</div>

JavaScript

/*jslint browser: true */
/*global google */
function toRad(value) {
    "use strict";
    /** Converts numeric degrees to radians */
    return value * (Math.PI / 180);
}

function getDistanceFromLatLonInKm(lat1, lon1, lat2, lon2, unit) {
    "use strict";
    var a, c, d, R, dLat, dLon;
    R = (unit === 'mi') ? 3958.75587 : (unit === 'ft') ? 20902230.9711286 : 6371; // Mean radius of the earth in km
    dLat = toRad(lat2 - lat1); // toRad below
    dLon = toRad(lon2 - lon1);
    a = Math.sin(dLat / 2) * Math.sin(dLat / 2) + Math.cos(toRad(lat1)) * Math.cos(toRad(lat2)) * Math.sin(dLon / 2) * Math.sin(dLon / 2);
    c = 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1 - a));
    d = R * c; // Distance in km
    return d;
}

function calcDistance(checkCoords, lat, lng) {
    "use strict";
    var closestLatLng, distance = 700000, i, latlng;
    for (i = 0; i < checkCoords.length; i = i + 1) {
        latlng = checkCoords[i].split(",");
        if (getDistanceFromLatLonInKm(latlng[0], latlng[1], lat, lng) < distance) {
            distance = getDistanceFromLatLonInKm(latlng[0], latlng[1], lat, lng);
            closestLatLng = [latlng[0], latlng[1]];
        }
    }
    return closestLatLng;
}

function addMarker(lat, lng, title, map) {
    "use strict";
    var marker = new google.maps.Marker({
        position: new google.maps.LatLng(lat, lng),
        title: title
    });
    marker.setMap(map);
    return (lat + ',' + lng);
}

function show_map(lat, lng) {
    "use strict";
    var checkCoords = [], closestLatLng, latlng, map, myOptions;
    latlng = new google.maps.LatLng(lat, lng);
    myOptions = {
        zoom: 10,
        center: latlng,
        mapTypeId: google.maps.MapTypeId.ROADMAP
    };
    map = new google.maps.Map(document.getElementById("map_container"), myOptions);
    checkCoords[0] = addMarker(51.477118, -0.000732, 'Royal Observatory, Greenwich, London', map);
    checkCoords[1] = addMarker(49, 1, 'Near Royal Observator', map);
    checkCoords[2] =...