Can you help me with the program?

Question

Hello everyone! I've just started to learn JS course and have the problem with if starement. My program works fine until I pressing ok with blank prompt or writiting a letter instead of number the "else if (age === isNaN(age) || age === null)" statemnt doesn't work. Can you help me, please?

var age = prompt("Please enter your age", "");

if (age < 18) {
alert("You can't come in");
} else if (age >= 18 && age < 21) {
alert("You can come in but can't drink");
} else if (age => 21) {
alert("You can come in and drink");
} else if (age === isNaN(age) || age === null) {
alert("Enter a valid number" );
}

Answer 1

Sorry, I forgot! Here's how to check for NaN:
if (isNaN(age))

Answer 2

Check for an empty string instead:
else if (age === "")

Answer 3

You can't say if(age===isNaN(age)). isNaN as a function is going to return a boolean (true or false). So simply say if(isNaN(age)). Otherwise you will always get false when comparing to age unless the user enters true for the prompt.

I don't know about the null entry.

Answer 4

You want the program to say "Enter a valid number" when the user types an input that is not a number?

Answer 5

It doesn't work too. Please test your code before posting here. I'm starting to think that you're fooling me

Answer 6

I think best way is to nest your if statements in another if (age>0)...else...enter valid number

var age= prompt("Please enter your age", "");

if(age>0){

if (age < 18) {
alert("You can't come in");
} else if (age >= 18 && age < 21) {
alert("You can come in but can't drink");
} else if (age => 21) {
alert("You can come in and drink");
}
}
else {
alert("Enter a valid number" );
}

doing that you can avoid blank inputs and letter inputs

Answer 7

No, it doesn't work

Answer 8

still not working :(

Answer 9

What is isNaN defined as?

Answer 10

mistake1:age>=21;mistake2:(age==isNaN(age)||age==null)
you try it

Answer 11

Tested it. Nothing changed

Answer 12

my language is C#.....i think i'm not good for help......

Answer 13

So your problem is that it doesn't work when you input a blank prompt or letters?

Answer 14

yes

Answer 15

That's because you've programmed it to where it only accepts numerical inputs

Answer 16

Check if you have defined all your variables

Answer 17

else if (age==(age)||age==null)

Answer 18

Why I see JS questions under python course?