Switch Case not showing correct results

Question

Here is my script

var marks = 11;
switch (marks) {
  case (marks < 20):
    console.log('Yes Freaking Failed');
    break;
  case (marks > 20):
    console.log('Ahh Its Ok');
    break;
  case (marks > 80):
    console.log('Whooping');
    break;
  default:
    console.log('Cant say u maybe Flunked');
    break;
}

I think it should display 'Yes Freaking Failed' because the marks are less than 20. But it shows 'Cant say u maybe Flunked'

Why is that?

Answer 1

When you write

switch (x) {
case(y):
    ...
}

it's equivalent to testing

if (x == y) {
    ...
}

So

case (marks < 20):

means:

if (marks == (marks < 20)) {

You can't use case for range tests like this, you need to use a series of if/else if:

if (marks < 20) {
    console.log('Yes Freaking Failed');
} else if (marks < 80) {
    console.log('Ahh Its OK');
} else {
    console.log('Whooping');
}

Also notice that if it worked the way you thought, it could never execute marks > 80, because that would also match marks > 20, and the first matching case is always executed.

There's no need for the Cant say u maybe flunked case, because there are no other possibilities.

Answer 2

Technically it's not possible. Javascript makes it so.

If you need to compare, use if/else if/else.

Switch cases are for when you know you will have specific values.

var marks=11;
    switch(marks){
        case (11):
        console.log('It would go in here');
        break;
        case (42):
        console.log('If equal to 42');
        break;
        case (80):
        console.log('if equal to 80.');            
        break;

        default:
        console.log('Cant say u maybe Flunked');
        break;
    }

Answer 3

Your code is equivalent to:

var marks=11;
switch(marks){
    case (true):
    console.log('Yes Freaking Failed');
    break;
    case (false):
    console.log('Ahh Its Ok');
    break;
    case (false):
    console.log('Whooping');    
    break;          
    default:
    console.log('Cant say u maybe Flunked');
    break;
}

marks is not true and is not false - so switch goes to default.

Answer 4

when you use switch statement, you are evaluating marks and compare the values of marks with the cases. And you have the following cases: 1, 0, 0, default. It's because (marks<20) evaluates to true which is 1, and the other two are false, which is 0. So you should do if and else if in your case.