Question

我试图制作一个基本计算器，根据从下拉菜单中选择的运算符进行数学计算，但它不起作用。我不确定为什么它不起作用。我试图接收所选项目的索引，而不是实际文本。

我的代码：

var numOne = document.getElementById("num-one");
var numTwo = document.getElementById("num-two");
var menu = document.getElementbyId("menuType"); // feeling like the error is here
var selection = menu.options[menu.selectedIndex].value; // or here
var userAnswer = document.getElementById("user-Answer");


numOne.addEventListener("input", math);
numTwo.addEventListener("input", math);

function math() {

    var one = parseFloat(numOne.value) || 0;
    var two = parseFloat(numTwo.value) || 0;
    var userSelect = selection

    if (userSelection == 1){
    userAnswer.innerHTML = one + two;
}
        else if (userSelection == 2){
                userAnswer.innerHTML = one - two;
            }

            else else if (userSelection == 3){
                    userAnswer.innerHTML = one * two;
            }

                else else else if (userSelection == 2){
                        if (two == 0){
                            alert("Error, cannot divide by 0");
                        }
                        else
                        userAnswer.innerHTML = one / two;
            }


}

Answer 1

您可以使用selectedIndex在下拉列表中返回所选选项的索引。

例如：document.getElementById("numOne").selectedIndex = "1";

如何在Javascript中获取下拉菜单索引值？

1 个答案: