JS去掉所有select标签的disabled属性

html代码

<form role="form" action="/save_element/" method="post" id="obj_form" onsubmit="return select_disable()">
{% csrf_token %}
    <select class="form-control" name="obj_find_type" id="{{ elements.type_select_id }}" style="border: none;outline:medium;width: 250px;" disabled>
        {% for find_type in find_type_list %}
             {% if elements.type == find_type %}
                <option value = {{ find_type }} selected="selected" >{{ find_type }}</option>
             {% else %}
                <option value = {{ find_type }}>{{ find_type }}</option>
             {% endif %}
        {% endfor %}
    </select>
    <div class="well well-sm" style="text-align:center">
        <button id="do_save" type="submit" class="btn btn-primary btn-flat m-b-10 m-l-5">保存</button>
    </div>
</form>

想要把form里面的所有select 标签的disabled 都去掉。
JS代码如下：

<script type="text/javascript">

function select_disable(){
    //先获取所有的select标签对象
    var select_name = document.getElementsByTagName("select");
    //逐个遍历select
    for(var i=0; i<select_name.length; i++){
        //select_name是一个数组
        //获取select的id值
        var select_id = select_name[i].id;
        //使用id值操作标签属性disabled
        $("#" + select_id).attr("disabled",false);
    }
}

</script>