事件监听器中的JavaScript回调

Question

I am currently trying to implement a system where a callback is triggered from within an event listener (code below). When I run the code, I get the error "callback is not a function", which I believe to be because the variable callback is not defined by the event listener.

function playSound(no, callback) {
var noOfSounds = sound().length;
if(no == "random" || no == undefined) {
    act("There are "+noOfSounds+" Sounds");
    var randomNo = Math.floor(Math.random() * noOfSounds);
    act("Will use no."+randomNo);
    playSound(randomNo);
} else {
    sound()[no].addEventListener("ended", function() {

        callback();

    });
    sound()[no].play();
}}

Answer 1

I think your problem is the way you are calling the function. If I look at line 10 you are saying

 playSound(randomNo)

It should be

 playSound(randomNo, function(){
    //code to execute in callback
});

This is because you are calling trying to use callback which is a function and should be added to the input parameters when calling the method.