JSFiddle - React, Tailwind, and code Playground

HTML

<select id="test">
  <option value="">请选择</option>
  <option value="1">选项一</option>
  <option value="2">选项二</option>
</select>

<input type="checkbox" id="flag" value="1"
      onchange="change(this, 'test')"/>  
      
      <p id="show">xx</p>

JavaScript

function change(self, targetId) {
        if ($(self).is(':checked')) {
            $("#" + targetId).val("44");
            $("#" + targetId).attr("disabled", true);  
        }
        else {
            $("#" + targetId).attr("disabled", false);
        }
        
        $("#show").html($("#" + targetId).val());
    }