使用 switch 接收未知数据类型，接收对象时出现问题

Question

在下面的代码中，我试图创建一个 switch 语句，它接受以下输入：34, '34', {input: 34}, hello, ["hello"]

并在每个输入中返回数字 34，我需要的情况是：

If given a number, return the number
If given a string, convert it to a number and return the result
If given an object, return the value of the input property
Otherwise, throw an error: "Unexpected data type"

我遇到了对象输入问题。非常感谢！

function parseNumber(unknown) {
  switch(unknown) {
    case 34:
        return unknown;
    
    case '34':
        return parseInt(unknown);
      
    case unknown.input: 
        return unknown.input;
    
    default:
        throw new Error("Unexpected data type");
  }
}

Answer 1

您可以在 switch 案例中使用typeof result 来确定输出：

/*If given a number, return the number
If given a string, convert it to a number and return the result
If given an object, return the value of the input property
Otherwise, throw an error: "Unexpected data type"*/


function parseNumber(unknown) {
  const type = typeof unknown;
  //typeof null is object so throwing error
  if (!unknown) throw new Error("Unexpected data type");
  //for non numeric strings throwing error
  if (type === "string" && Object.is(+unknown, NaN)) throw new Error("Unexpected data type");
  //typeof Array is object so excluding arrays
  if (Array.isArray(unknown)) throw new Error("Unexpected data type");
  if (type === "object" && !unknown.hasOwnProperty("input")) throw new Error("Unexpected data type");
  
  switch (type) {
    case "number":
      return unknown;
    case "string":
      return +unknown;
    case "object":
      return unknown.input;
    default:
      throw new Error("Unexpected data type");
  }
}
console.log(parseNumber(34));
console.log(parseNumber('34'));
console.log(parseNumber({input: 34}));
//Error cases
try{
console.log(parseNumber("hello"));
}catch(e){console.error(e)}

try{
console.log(parseNumber());
}catch(e){console.error(e)}

try{
console.log(parseNumber(() => "hello"));
}catch(e){console.error(e)}

try{
console.log(parseNumber([34]));
}catch(e){console.error(e)}

try{
console.log(parseNumber({"foo": "bar"}));
}catch(e){console.error(e)}