返回元素集合的jQuery选择器在没有找到匹配时具有 zero 元素，这是它的设计方式。您可以使用length属性来检查是否获得了元素

if($('yourselector').length)
{
    //You got one or more elements
}
else
{
   //You haven't got any element.
}

• 定义 *

jQuery.fn.extend({
      notEmpty: function (atLeast) {
          const len = atLeast || 1;
          if (this.length < len)
              throw `unable to find ${len} element with selector : 
              '${this.selector}'. ${this.length} element is found.`;
          return this;
      }
  });

• 使用 *

let el = $(".at_least_one_element_selector").notEmpty();       
let el = $(".at_least_5_element_selector").notEmpty(5);