Trouble understanding if statement code

Question

I am going through a book about HTML5 and there are two lines of code I cannot quite understand

var mp3Support,oggSupport;
var audio = document.createElement('audio');
if(audio.canPlayType) {
        mp3Support = "" != audio.canPlayType('audio/mp3');
}

So, first you create an audio element and check if canPlayType method can be used? Then, the code inside the if statement is some kind of ternary operation?

The audio.canPlayType('audio/mp3') outputs 'probably' and mp3Support is set to '' but after that line mp3Support outputs true. Any tips would be much appreciated.

Quentin · Accepted Answer · 2015-02-03 16:49:46Z

2

So, first you create an audio element

Yes

and check if canPlayType method can be used?

The check is to see if canPlayType is a true value, but that amounts to the same thing in practical terms.

Then, the code inside the if statement is some kind of ternary operation?

No.

audio.canPlayType('audio/mp3') can return a number of values, one of which is an empty string.

"" != audio.canPlayType('audio/mp3'); tests to see if it not an empty string (and evaluates as true or false)

mp3Support = then is just assigned that true or false

It could be more clearly written as:

mp3Support = ("" != audio.canPlayType('audio/mp3'));

answered Feb 3, 2015 at 16:49

Quentin

949k136 gold badges1.3k silver badges1.4k bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

kidA Over a year ago

Thank you for the really thorough explanation!

Vijay · Accepted Answer · 2015-02-03 16:48:59Z

1

 mp3Support = "" != audio.canPlayType('audio/mp3');

This combines a variable initialization with boolean expression.

in other way:

if(audio.canPlayType('audio/mp3')!="")
{
  mp3Support=true;
}
else
{
  mp3Support=false;
}

answered Feb 3, 2015 at 16:48

Vijay

3,0231 gold badge17 silver badges24 bronze badges

Collectives™ on Stack Overflow

Trouble understanding if statement code

2 Answers 2

1 Comment

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

1 Comment

Comments

Your Answer

Sign up or log in

Post as a guest

Related