去除对象中的null值属性

function removeNull(option) {
    if (!option) {
        return;
    }
    for (var attr in option) {
        if (option[attr] === null && attr !== 'teacherId') {
            delete option[attr];
            continue;
        }
        if (typeof (option[attr]) == "object") {
            removeNull(option[attr]);
        }
    }
}