Function to update javascript object with contents of another object

update.js

function update(obj) {
    for (var i=1; i<arguments.length; i++) {
        for (var prop in arguments[i]) {
            var val = arguments[i][prop];
            if (Object.prototype.toString.call(val) === '[object Array]') { //Array
                obj[prop] = [];
                update(obj[prop], val);
            }
            else if (typeof val == 'object' && !(val instanceof Date) && val != null) { //Object
                if (typeof obj[prop] != 'object' || obj[prop] == null) {
                    obj[prop] = {};
                }
                update(obj[prop], val);
            }
            else //Everything else
                obj[prop] = val;
        }
    }
    return obj;
}

// Minified:
// function update(t){for(var e=1;e<arguments.length;e++)for(var r in arguments[e]){var a=arguments[e][r];"[object Array]"===Object.prototype.toString.call(a)?(t[r]=[],update(t[r],a)):"object"!=typeof a||a instanceof Date||null==a?t[r]=a:(("object"!=typeof t[r]||null==t[r])&&(t[r]={}),update(t[r],a))}return t}

// Example:
// update({ "a": 1 , "b": 2 }, { "a": 4 , "c": 3 })  ->  { "a": 4, "b": 2, "c": 3 }