javascript实现避免页面按钮重复提交

function preventAjax(obj,num){
            obj.disabled = true;
            var num = num;
            var types =obj.type;
            if(types == 'submit'){
                var text = obj.value;
                var time1 = setInterval(function(){
                    obj.value = num;
                    num--;
                    if(obj.value <= 0 ){
                        clearInterval(time1);
                        obj.disabled = false;
                        obj.value = text;
                    }
                },1000);
            }else{
                var text = obj.innerHTML
                var time1 = setInterval(function(){
                    obj.innerHTML = num;
                    num--;
                    if(obj.innerHTML <= 0 ){
                        clearInterval(time1);
                        obj.disabled = false;
                        obj.innerHTML = text;
                    }
                },1000);
            }
        }