Simple if else function not returning as expected

Question

Please could someone tell me where I'm going wrong here, I know it's something simple I'm missing so forgive my ignorance but I can't find the error.

let day = "Monday"

function alarmTime(day) {
  if (day == "Saturday") {
    return "Set alarm for 8:00am"
  } else if (day == "Friday") {
    return "Set alarm for 5:35am"
  } else if (day == "Sunday" || "Thursday") {
    return "Set alarm for 4:50am"
  } else {
    return "Set alarm for 7:00am"
  }
}

console.log(alarmTime(day));

if day is Mon, Tue, Wed then it returns 4:50am??? Why?? It should reach the final else statement and return 7:00am ‍♀️

"[How to debug small programs](https://ericlippert.com/2014/03/05/how-to-debug-small-programs/)" — Uwe Keim, Jan 12 '23 at 10:45
Use linters like [ESLint](//eslint.org/play) or [JSHint](//jshint.com) to find problems with your code immediately. Relevant linter warning: [_“Unexpected constant condition”_](//eslint.org/docs/latest/rules/no-constant-condition). — Sebastian Simon, Jan 12 '23 at 10:54

score 2 · Answer 1 · answered Jan 12 '23 at 10:44

2

Because day == "Sunday" || "Thursday" evaluates to Thursday. Since if ("Thursday") evaluates to true, it always enters in this block.

What you want to have is day == "Sunday" || day == "Thursday"

answered Jan 12 '23 at 10:44

Aid Hadzic

578
3
10

score 0 · Answer 2 · answered Jan 12 '23 at 10:46

0

The or operator, ||, accepts two conditions, not two possible values for a variable

ie: foo == "hello" || foo == "hi"

not foo == "hello" || "hi" as that just evaluates "hi" which returns true like all strings

answered Jan 12 '23 at 10:46

TorNato

305
2
12

score 0 · Answer 3 · answered Jan 12 '23 at 10:46

Below is the updated fuction. It returns 7:00am

function alarmTime(day) {
  if (day == "Saturday") {
    return "Set alarm for 8:00am"
  } else if (day == "Friday") {
    return "Set alarm for 5:35am"
  } else if (day == "Sunday" || day == "Thursday") {
    return "Set alarm for 4:50am"
  } else {
    return "Set alarm for 7:00am"
  }
}

Filip Huhta · Answer 4 · 2023-01-12T10:58:08.547

The issue is that the third else if statement does not have a condition for the day to be "Sunday" or "Thursday". Instead, it has a condition for day to be "Sunday" or the boolean value true, which will always evaluate to true. This causes the code to always return "Set alarm for 4:50am".

To fix this, you can change the third else if statement to:

else if (day == "Sunday" || day == "Thursday")

Example with fixed code:

let day = "Monday"

function alarmTime(day) {
  if (day == "Saturday") {
    return "Set alarm for 8:00am"
  } else if (day == "Friday") {
    return "Set alarm for 5:35am"
  } else if (day == "Sunday" || day == "Thursday") {
    return "Set alarm for 4:50am"
  } else {
    return "Set alarm for 7:00am"
  }
}

console.log(alarmTime(day));

score 0 · Accepted Answer · answered Jan 12 '23 at 10:49

day == "Sunday" || "Thursday"

This says, if the day is "Sunday" return true, else return "Thursday". "Thursday" is a string, so JavaScript converts it to true. See here

Look at the || operator like this (day == "Sunday") || ("Thursday")

You want to say:

day == "Sunday" || day =="Thursday"

Bonus tip: use === instead of == This is the best way to put it:

day === "Sunday" || day ==="Thursday"

Simple if else function not returning as expected

5 Answers5