`if` statement comparing return value of `prompt` to number is never executed

Question

I am writing a game and I have this problem: the last if statement (and all its else if statements) are never executed.

Here is the code that doesn’t work:

const compare = prompt("1.mars, 2.jupiter, 3.moon")

if (compare === 2) {
  confirm("your airplane crashed and you died")
} else if (compare === 1) {
  confirm("you arrived safely")
} else if (compare === 3) {
  confirm("you survived an airplane crash but you need to escape")
}

``prompt`` queries a *string*, but you compare with *integer*s (e.g.: ``'1' === 1`` is equivalent to ``false``) — Binkan Salaryman, Jul 06 '15 at 08:02
you could change your if statements to just use `==` instead of `===`, therefore the type doesn't have to match too: `if (compare == 2)` ... etc — duncan, Jul 06 '15 at 08:09

score 1 · Answer 1 · answered Jul 06 '15 at 08:11

1

As @Binkan Salaryman very accurately pointed out, prompt is returning a String ('1', '2', etc.).

Either use == to compare untyped values like compare==2 or compare with the correct type: e.g. compare==='2'

answered Jul 06 '15 at 08:11

SDekov

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`==` and `!=` are almost [never recommended](https://stackoverflow.com/q/359494/4642212). They’re not always intuitively transitive since they oftentimes unnecessarily perform type coercion. Always use `===` and `!==` instead. Either use `Number(prompt(`…`))` or compare against strings. – Sebastian Simon Apr 05 '21 at 07:25

score 0 · Answer 2 · answered Jul 06 '15 at 08:13

0

use Equality operator( == ) instead of Strict equality ( === ) operator. With ===, comparison returns true only if both the operands same in type as well. In your case, the result of prompt returns string, and

compareInt === 2; // '2' === 2

returns false as you are checking for string and number to be same.

'2' === 2 returns false as type checking is also done
'2' == 2 returns true as no type checking

answered Jul 06 '15 at 08:13

Sudhir Bastakoti

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_“as no type checking”_ is wrong. `==` and `!=` are almost [never recommended](https://stackoverflow.com/q/359494/4642212). They’re not always intuitively transitive since they oftentimes unnecessarily perform type coercion. Always use `===` and `!==` instead. Either use `Number(prompt(`…`))` or compare against strings. – Sebastian Simon Apr 05 '21 at 07:28

score 0 · Answer 3 · answered Jul 06 '15 at 08:16

I made a little demo. Refactored your code a little. Demo

The main problem as some people have pointed out is that prompt returns a string even if you write a number.

You'll need to convert this string to an int using parseInt() function.

if(jack === 'yes'){
    var compare = parseInt(prompt("1.mars, 2.jupiter, 3.moon"));
    switch(compare){
        case 2: confirm("your airplane crashed and you died")
            break;
        case 1: confirm("you arrived safely")
            break;
        case 3: confirm("you survived an airplane crash but you need to escape")
            break;
        default:
            confirm("An error occured");
    }
}

Please use `parseInt` [_with_ the second parameter, `10`](https://stackoverflow.com/q/16880327/4642212). Consider using [`Number`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number#Function_syntax) or [`parseFloat`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/parseFloat) instead. — Sebastian Simon, Apr 05 '21 at 07:27

Adam Tychoniewicz · Answer 4 · 2015-07-06T08:11:11.030

-1

Try:

compareInt = parseInt(compare)

Final code looks like:

var compare = prompt ("1.mars,2.jupiter,3.moon")
var compareInt = parseInt(compare);
if (compareInt===2) {confirm ("your airplane crashed and you died")}
else if (compareInt===1) {confirm ("you arrived safely")}
else if (compareInt===3){
confirm("you survived an airplane crash but you need to escape")}

edited Jul 06 '15 at 08:11

answered Jul 06 '15 at 08:04

Adam Tychoniewicz

648
6
7

score -1 · Answer 5 · edited Jul 06 '15 at 08:15

-1

for work your code you don't need to strict check by === you can use the simple comparison with ==

because === will compare both's type also as well as the value
while == only compares the value

edited Jul 06 '15 at 08:15

R3tep

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answered Jul 06 '15 at 08:11

Himesh Aadeshara

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`if` statement comparing return value of `prompt` to number is never executed

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