JavaScript Coercion: Console vs Script

Question

today, I encountered something rather strange. Consider the following code (which I use to sync a range slider with an input element):

// val = "50"
// other_val = 100  
if( val > other_val ){
    console.log(val + '>' + other_val); // => 50 > 100
    console.log( val > other_val); // => true
    $input_max.val( other_val );
}

How did that happen? When I type

"50" > 100

into my console (Chrome & FireFox), it says false, which is what I expected. I fixed the resulting bug with parseInt(), but I still don't know why this happened. Also, I don't know why I can't reproduce it outside of this script.

Any ideas? :)

Cheers!

Update:

As Bergi pointed out, it was "50">"100", and not "50" > 100. Thank you very much for that idea. Now, my real question seems to be:

Why does this return true:

"50">"100" // => true

You want to know why `val + '>' + other_val` resulted `"50 > 100"` ? — DontVoteMeDown, Mar 23 '15 at 14:58
@DontVoteMeDown Looks like OP wants to know, why `"50">100` logs `true` from a script, but `false` when you run it directly in the console. — Teemu, Mar 23 '15 at 15:00
it can never happen. `"50"` is converted to `50` and `50 > 100` results in `false`, so the if block is never executed. — Amit Joki, Mar 23 '15 at 15:01
Are you sure that it's not `"100"` instead of `100`? Because `"50" > "100"`. — Bergi, Mar 23 '15 at 15:01
It was. That's the trouble I'm having with this. Has to be something else. But what? — CunningFatalist, Mar 23 '15 at 15:01
So why is "50" > "100"? Edit: Oh, of course, it's a string compare sorting by character. And '5' > '1'. — EasyPush, Mar 23 '15 at 15:03
@Bergi: Exactly. Thanks. So "50">"100" does not behave as I expected either. — CunningFatalist, Mar 23 '15 at 15:03

score 1 · Accepted Answer · answered Mar 23 '15 at 15:07

1

The answer to your edited question is that when you compare strings it compares character by character from the beginning of the string. And the character 5 is "larger" than 1.

answered Mar 23 '15 at 15:07

EasyPush

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Tested it, "50">"100" returns true, "050">"100" returns false. Thanks, mate! – CunningFatalist Mar 23 '15 at 15:09

JavaScript Coercion: Console vs Script

1 Answers1