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// http://stackoverflow.com/questions/23808928/javascript-elegant-way-to-check-nested-object-properties-for-null-undefined

get = function(obj, key) {
    return key.split(".").reduce(function(o, x) {
        return (typeof o == "undefined" || o === null) ? o : o[x];
    }, obj);
}
// Usage:
get(user, 'loc.lat')     // 50
get(user, 'loc.foo.bar') // undefined


// Or, to check only if a property exists, without getting its value:
has = function(obj, key) {
    return typeof get(obj, key) !== 'undefined';
}
// Usage:
if(has(user, 'loc.lat')) {
  // something
}