getProperty.js

function getProperty (prop, obj) {
    var p;
    var o = obj;
    var props = prop.split('.');

    while (props.length) {
        p = props.shift();
        o = o[p];
        if (typeof o === 'undefined') {
            break;
        }
    }
    return o;
}

var x = {a:{b:{c:{d:123}}}};

console.log( getProperty('a.b.c', x) );