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如何设置下拉菜单以在javascript中的onclick事件之后进行选择

[英]how to set dropdown to select after onclick event in javascript

在下拉菜单中有一个选项的情况下,我有一个下拉菜单,在按钮上有一个onclick事件,在从下拉菜单中进行选择并单击按钮后,如何将下拉菜单设置为JavaScript选择的默认菜单。

 <select id="userType">
              <option value="Select" disabled selected 
              id="myDefault">Select</option>
              <option value="1">Games</option>
              <option value="2">Movies</option>
           </select>
 <button type="button" name="button"onclick="addOption()">Send</button>

function addOption(){
 if (userType.value === "Select") {
    alert("Please select correct option");
 }
 else{
    console.log(userType.options[userType.selectedIndex].value);
 }
 document.getElementById('userType').value = "Select";

}

非常简单。 只需通过id选择输入,并将其值设置为默认值即可。

 function addOption(){ // Do stuff...and then: document.getElementById('userType').value = "Select"; } 
 <select id="userType"> <option value="Select" disabled selected id="myDefault">Select</option> <option value="1">Games</option> <option value="2">Movies</option> </select> <button type="button" name="button"onclick="addOption()">Send</button> 

这是您的工作代码:

 $("button").click(function() { $('select').prop('selectedIndex', 0); }); 
 <script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script> <select id="userType"> <option value="Select" disabled selected id="myDefault">Select</option> <option value="1">Games</option> <option value="2">Movies</option> </select> <button type="button" name="button">Send</button> 

 <html> <body> <form id="myForm"> <select id="a"> <option value="volvo">Volvo</option> <option value="saab">Saab</option> <option value="opel">Opel</option> <option value="audi">Audi</option> </select> <br> <input type="button" onclick="myFunction()" value="Reset"> </form> </body> </html> <script> function myFunction() { document.getElementById('a').selectedIndex = 0; } </script> 

尝试这个

您可以将change事件附加到<select>元素,声明一个变量,在事件处理程序中将变量设置为true以验证是否发生了change事件。 click <button> ,如果Boolean值为true ,请将select .selectedIndex属性设置为0 ,将Boolean设置为false

 <script> var changed, select; function addOption() { if (changed) { select.selectedIndex = 0; changed = false; } } onload = function() { select = document.getElementById("userType"); select.onchange = function() { changed = true; } } </script> <select id="userType"> <option value="Select" disabled selected id="myDefault">Select</option> <option value="1">Games</option> <option value="2">Movies</option> </select> <button type="button" name="button" onclick="addOption()">Send</button> 

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