Analysis on the implementation method of jQuery select automatic selection function

This article analyzes the implementation method of jQuery select automatic selection function through examples. Share it with everyone for your reference, the details are as follows:

//筛选
var typeid = "<!--{$typeid}-->";
var bigclassid = "<!--{$bigclassid}-->";
var smallclassid = "<!--{$smallclassid}-->";
$("#typeid option[value="+typeid+"]").attr("selected",true);
$("#typeid").change();
$("#bigclassid option[value="+bigclassid+"]").attr("selected",true);
$("#bigclassid").change();
$("#smallclassid option[value="+smallclassid+"]").attr("selected",true);

After getting the value, set it to be automatically selected.

After selecting, call the change() method. The change method will display the next level select box. Then select it again and call the change() method. In this way, all the three-level select boxes are displayed and selected by default.

$(document).ready(function(){
  //ajax级联
  $("#typeid").change(function(){
    var id = $(this).val();
    setbigclass(id);
  });
  $("#bigclassid").change(function(){
    var id = $(this).val();
    setsmallclass(id);
  });
  $("#screen_submit").click(function(){
    $("#screenform").submit();
  });
});
function setbigclass(id){
    var res = ajaxgetbigclass(id);
    if(res){
      myobj = eval(res);
      var strHtml="<option value=0>全部大类</option>";
      for(var i=0;i<myobj.length;i++){
          strHtml+="<option value=&#39;"+myobj[i].id+"&#39;>"+myobj[i].name+"</option>";
      }
      $("#bigclassid").html(strHtml);
      $("#bigclassid").show().change();
    }else{
      $("#bigclassid").html(&#39;<option value=""></option>&#39;).hide();
      $("#smallclassid").html(&#39;<option value=""></option>&#39;).hide();
    }
}
function setsmallclass(id){
    var res = ajaxgetsmallclass(id);
    if(res){
      myobj = eval(res);
      var strHtml="<option value=0>全部子类</option>";
      for(var i=0;i<myobj.length;i++){
          strHtml+="<option value=&#39;"+myobj[i].id+"&#39;>"+myobj[i].name+"</option>";
      }
      $("#smallclassid").html(strHtml);
      $("#smallclassid").show();
    }else{
      $("#smallclassid").html(&#39;&#39;).hide();
  }
}