Question

所以我必须制作一些代码，当用户输入1-4中的数字时，它会执行+ - *或/，具体取决于他们选择的数字。

console.log("Calculator program");                                      
console.log("1. Add numbers");
console.log("2. Subtract numbers");
console.log("3. Multiply numbers");
console.log("4. Divide numbers");

var choice = prompt ("What is your choice?");

if (choice == 1)
{
  console.log(number1 + number2);
}
if (choice == 2)
{
  console.log(number1 - number2);
}
if (choice == 3)
{
  console.log(number1 * number2);
}
if (choice == 4)
{
  console.log(number1 / number2);
}


var number1 = prompt("Type in a number"); 
var number2 = prompt("Type in another number");

用户打算在选择功能后输入数字，但是当用户键入第一个数字时，会出现NaN。

我认为这是因为用户在2个数字中甚至没有类型，但我需要用户最后输入数字。

非常感谢任何帮助和建议，谢谢

Answer 1

你需要接受if else逻辑之前的数字，并将这些数字转换为int或float进行计算（默认情况下用户提示符为字符串）：

＆＃13;

console.log("Calculator program");                                      
console.log("1. Add numbers");
console.log("2. Subtract numbers");
console.log("3. Multiply numbers");
console.log("4. Divide numbers");

var number1 = prompt("Type in a number"); 
var number2 = prompt("Type in another number");
number1 = parseFloat(number1);
number2 = parseFloat(number2);
var choice = prompt ("What is your choice?");

if (choice == 1)
{
  console.log(number1 + number2);
}
if (choice == 2)
{
  console.log(number1 - number2);
}
if (choice == 3)
{
  console.log(number1 * number2);
}
if (choice == 4)
{
  console.log(number1 / number2);
}

＆＃13;

Answer 2

作业没有提升，所以在你使用它们时没有定义number1和number2

Answer 3

声明为全局变量。在条件之前添加提示符。数字是一个字符串output.use parseInt()转换为整数。如果您需要使用parseFloat()

进行浮动使用

＆＃13;

console.log("Calculator program");                                      
console.log("1. Add numbers");
console.log("2. Subtract numbers");
console.log("3. Multiply numbers");
console.log("4. Divide numbers");
var number1=0;
var number2=0
var choice =0;
choice = parseInt(prompt ("What is your choice?"));

number1 = parseInt(prompt("Type in a number")); 
number2 = parseInt(prompt("Type in another number"));
if (choice == 1)
{
  console.log(number1 + number2);
}
if (choice == 2)
{
  console.log(number1 - number2);
}
if (choice == 3)
{
  console.log(number1 * number2);
}
if (choice == 4)
{
  console.log(number1 / number2);
}

＆＃13;

Answer 4

var x = function() {
console.log("Calculator program");                                      
console.log("1. Add numbers");
console.log("2. Subtract numbers");
console.log("3. Multiply numbers");
console.log("4. Divide numbers");

var choice = prompt ("What is your choice?");


var number1 = Number(prompt("Type in a number")); 
var number2 = Number(prompt("Type in another number"));

if (choice == 1)
{
  console.log(number1 + number2);
}
if (choice == 2)
{
  console.log(number1 - number2);
}
if (choice == 3)
{
  console.log(number1 * number2);
}
if (choice == 4)
{
  (number2 !== 0) && console.log(number1 / number2);
}

}

JavaScript意外的NaN？

4 个答案: