HTML and CSS Reference
In-Depth Information
to play the sound in the game. We then call
itemLoaded()
so that we can increment the
loadCount
variable in the
Space Raiders
game.
function
function
loadShootSound
(
url
) {
var
var
request
=
new
new
XMLHttpRequest
();
request
.
open
(
'GET'
,
url
,
true
true
);
request
.
responseType
=
'arraybuffer'
;
request
.
onload
=
function
function
() {
audioContext
.
decodeAudioData
(
request
.
response
,
function
function
(
buffer
) {
shootSoundBuffer
=
buffer
;
itemLoaded
();
},
onSoundError
);
};
request
.
send
();
}
function
function
onSoundError
(
e
) {
alert
(
"error loading sound"
)
}
We then create a similar function like the above for the “explode” sound. The only difference
isthatweset
explodeSoundBuffer
tothevalueofthebufferinthesuccesscallbackfunction:
explodeSoundBuffer
=
buffer
;
Now, inside the game when we want to play a sound, we call the
playSound()
function,
passing the name of the sound buffer we want to play:
playSound
(
shootSoundBuffer
);
The
playSound()
function is now totally different than the one we created in the previous
iteration of
Space Raiders
because we don't have to manage multiple copies of each sound.
First, we create an instance of
AudioBufferSourceNode
by calling
audioCon-
text.createBufferSource()
and save it in a variable named
source
. This object will hold
the sound that we will be playing. We set the
buffer
property of
source
to the buffer that
we passed into the function. Again, this buffer represents one ofoursoundsin memory (shoot
or explode). We then call the connect function of
audioContext
to set the destination for
the sound. For our purposes, we are using the default destination value, which should be the
speakers on your computer. Finally, we call the
noteOn()
function of the source, passing
0
,
which means “start playing immediately.”
You can call the
noteOn()
function on an instance of
AudioBufferSourceNode
only once.
After that, it will never play a second time. You need to create another instance if you want
