如何在 JavaScript 中的 OnChange() 事件中使用 If Else？

Question

这是我的 HTML 代码：

<select id="stand" onchange="myFun2()">

                <option value="platinumGallery">Platinum Gallery</option>

                <option value="superHospitalityStand">Super Hospitality Stand</option>

                <option value="northWestStand">North West Stand</option>

                <option value="eastStand">East Stand</option>

</select><br><br>

<label>Cost Of Ticket: </label>

<input id="costOfTicket" type="text" readonly>

和JS代码：

function myFun2(){

    var costOfTicket;

    var selectedStand = document.getElementById("stand").value;

    if(selectedStand = "platinumGallery"){

        costOfTicket = 25000;

    }

    else if(selectedStand = "superHospitalityStand"){

        costOfTicket = 20000;

    }

    document.getElementById("costOfTicket").value = costOfTicket;

}

每当onchange()事件发生时，我想Cost Of Ticket根据选择的值进行显示select。但它会在事件发生25000后显示onchange()，然后无论选择的值如何都不会改变。如何修正代码来完成上述任务？

Answer 1

让我告诉你。在 if-else 语句中，您不是在比较值，而是实际上是在分配值。因此，将 if-else 语句更改为：if(selectedStand == "platinumGallery"){&nbsp; &nbsp; &nbsp; &nbsp; costOfTicket = 25000;}else if(selectedStand == "superHospitalityStand"){&nbsp; &nbsp; &nbsp; &nbsp; costOfTicket = 20000;}

Answer 2

您在声明=中使用了if。您需要在`if 语句中使用==or===来使其作为条件起作用。function myFun2(){&nbsp; &nbsp; var costOfTicket;&nbsp; &nbsp; var selectedStand = document.getElementById("stand").value;&nbsp; &nbsp;&nbsp;&nbsp; &nbsp; if(selectedStand == "platinumGallery"){&nbsp; &nbsp; &nbsp; &nbsp; costOfTicket = 25000;&nbsp; &nbsp; }&nbsp; &nbsp; else if(selectedStand == "superHospitalityStand"){&nbsp; &nbsp; &nbsp; &nbsp;&nbsp;&nbsp; &nbsp; &nbsp; &nbsp; costOfTicket = 20000;&nbsp; &nbsp; }&nbsp; &nbsp; document.getElementById("costOfTicket").value = costOfTicket;}<select id="stand" onchange="myFun2()">&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; <option value="platinumGallery">Platinum Gallery</option>&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; <option value="superHospitalityStand">Super Hospitality Stand</option>&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; <option value="northWestStand">North West Stand</option>&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; <option value="eastStand">East Stand</option></select><br><br><label>Cost Of Ticket: </label><input id="costOfTicket" type="text" readonly>