jQuery method to get the child element object of this current object

As shown below:

<select id="city">
   <option value="beijing">北京</option>
   <option value="shanghai">上海</option>
   <option value="shenzhen">深圳</option>
</select>
$(function(){
  $("#city").change(function(){
    ①// 已获取select为当前this元素
  })
})

If you want to get the value of the selected option in ①, you can use the following method

$("#city option:selected").val(); //使用选择器
$(this).children('option:selected').val() //使用this

Sometimes we take it for granted and write $(this "a"), $ ("this a") etc., this is wrong