Fast & concise deep copy / deep clone / shallow copy in Javascript

deepCopy.js

var deepCopy = function (o) {
    var t, x, key
    t = Array.isArray(o) ? [] : {}
    for (key in o) {
        x = o[key]
        t[key] = (typeof x === "object" && x !== null && !(x instanceof Date)) ? deepCopy(x) : x
    }
    return t
}