为什么当我尝试在函数中添加一些结果时 console.log 打印到控制台 "undefined"？

Question

我尝试在 const getActualSleepHours() 中添加 getSleepHours() 以获得总和。但是 console.log 打印未定义，我不知道我做错了什么。谁能帮帮我？

const getSleepHours = day => {
  switch(day) {
    case 'monday':
      return 8;
      break;
    case 'tuesday':
      return 8;
      break;
    case 'wednesday':
      return 9;
      break;
    case 'thursday':
      return 9;
      break;
    case 'friday':
      return 7;
      break;
    case 'saturday':
      return 10;
      break;
    case 'sunday':
      return 9;
      break;
   }    
  };
   const getActualSleepHours = () => {
     getSleepHours('monday') +
     getSleepHours('tuesday') +
     getSleepHours('wednesday') +
     getSleepHours('thursday') +
     getSleepHours('friday') +
     getSleepHours('saturday') +
     getSleepHours('sunday');
           
     
     
  };
const getIdealSleepHours = () => {
  const idealHours = 8.5;
  return idealHours * 7;
};
console.log(getActualSleepHours());
console.log(getIdealSleepHours());

Answer 1

您错过了 return，您正在调用的函数没有 return 值，因此它 return 是每个执行的没有 return 值的 JS 函数returns, undefined

const getSleepHours = day => {
  switch(day) {
    case 'monday':
      return 8;
      break;
    case 'tuesday':
      return 8;
      break;
    case 'wednesday':
      return 9;
      break;
    case 'thursday':
      return 9;
      break;
    case 'friday':
      return 7;
      break;
    case 'saturday':
      return 10;
      break;
    case 'sunday':
      return 9;
      break;
   }    
  };
   const getActualSleepHours = () => 
     getSleepHours('monday') +
     getSleepHours('tuesday') +
     getSleepHours('wednesday') +
     getSleepHours('thursday') +
     getSleepHours('friday') +
     getSleepHours('saturday') +
     getSleepHours('sunday');

const getIdealSleepHours = () => {
  const idealHours = 8.5;
  return idealHours * 7;
};
console.log(getActualSleepHours());
console.log(getIdealSleepHours());

Answer 2

您没有在 getActualSleepHours 函数中返回任何内容。摆脱大括号，所以它来自

const getActualSleepHours = () => {
    getSleepHours("monday") +
    getSleepHours("tuesday") +
    getSleepHours("wednesday") +
    getSleepHours("thursday") +
    getSleepHours("friday") +
    getSleepHours("saturday") +
    getSleepHours("sunday");
};

至

const getActualSleepHours = () =>
    getSleepHours("monday") +
    getSleepHours("tuesday") +
    getSleepHours("wednesday") +
    getSleepHours("thursday") +
    getSleepHours("friday") +
    getSleepHours("saturday") +
    getSleepHours("sunday");

为什么当我尝试在函数中添加一些结果时 console.log 打印到控制台 "undefined"？

Why the console.log prints to the console "undefined" when I try to add some results in the function?

javascript

function

switch-statement

console.log

arrow-functions