如何使用javascript预选择select tag's选项

how to preselect select tag's option using javascript

本文关键字：选项 tag select 何使用 javascript 选择更新时间：2023-09-26

我有一个包含选择标签的表单，我想在单击上一页上的按钮后预填充该标签。我该怎么做呢?下面是表单代码:

<form method="post" name="registration" action="http://esafe.urdemo.net/user/login/signup" onsubmit="return checkform2();">
                                <input type="text" class="textbox"  placeholder="Enter First Name"   name="first_name" /> 
                               <input type="text" class="textbox"   placeholder="Enter Middle Name" name="middle_name" />
                               <input type="text" class="textbox"  placeholder="Enter Last Name" name="last_name" />
                               <input type="text" class="textbox"  placeholder="Select Date dd/mm/yyyy"  name="Date1" onblur="return checkdob(this);"/>
                               <input type="text" class="textbox"  placeholder="Enter Email Id" name="email" />
                               <input type="text" class="textbox"  placeholder="Enter Mobile No." name="mobile" />
                               <select name="plan" class="form-control"  style="width:90%">
                                    <option value="" selected="selected">Please Select</option>
                                    <option value="1">Pro</option>
                                    <option value="2">Premium</option>
                                    <option value="3">Elite</option>
                                    <option value="4">Magna</option>
                               </select>
 <div class="signinStrip">
  <span class="forgot"> <a href="#" id="resend_password_link"></a> </span>
   <input class="signin_submit" value="Submit" type="submit" />
    </div>
    </form>

这是按钮的代码

 <tr>
     <td class="title">&nbsp;</td>
     <td><p class="bottom"><a class="btn btn-primary" href="#" >Buy Now</a></p></td>
     <td><p class="bottom"><a class="btn btn-primary" href="#" >Buy Now</a></p></td>
     <td><p class="bottom"><a class="btn btn-primary" href="#" >Buy Now</a></p></td>
     <td><p class="bottom"><a class="btn btn-primary" href="#" >Buy Now</a></p></td>
    </tr>

如果你想选择基于按钮点击前一页的特定选项，那么你必须通过一些服务器端变量或通过地址url参数发送该值。如。第二页url必须是"http://yourdomain.com/page2?selected_value=temp"

然后在下一页javascript中你必须提取这个参数

function getParam(paramName) {
  return decodeURI(
    (RegExp(paramName + '=' + '(.+?)(&|$)').exec(location.search)||[,null])[1]
  );
} 
var selectedVal = getParam("elected_value");
document.getElementById(<your select box id>).value = selectedVal;