var getParam = function (key) {
    var arr = window.location.search.slice(1).replace(/\+/g, ' ').split('&');
    var result = undefined;
    for (var i = 0; i < arr.length; i++) {
        if (arr[i].split('=')[0] === key) {
            if (!result) {
                result = arr[i].split('=')[1];
            } else {
                result = [result].concat(arr[i].split('=')[1]);
            }
        }
    }
    return result;
}

------解决方案--------------------

探讨

result = [result].concat(arr[i].split('=')[1]);