当我尝试在函数中添加一些结果时，为什么 console.log 打印到控制台“未定义”？

Question

I try to add getSleepHours() in the const getActualSleepHours() to have a sum. But the console.log prints undefined and I don't know what I'm doing wrong. Could anyone help me?

 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

You missed the return, the function you're calling has no return value so it returns what every executed JS function with no return value 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

You're not returning anything in your getActualSleepHours function. Get rid of the braces so it goes from

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

to

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