I have a custom function and I want to add a callback function to it, i looked through the other questions but I couldn't really find the answer for my problem. So basically it looks like this:
function myfunction() {
// something
}
And I have a different function which I want to trigger as a callback, eventually i want to call myfunction like this:
myfunction(callback());
So can anyone please tell my the way to do this?
You would call it like this (passing the callback function as an argument):
myfunction(myCallbackFn);
Notice that there are no parentheses after the function name when passing a reference to the function as an argument. This does not invoke the function, but just passes a reference to it which can then be called later from within your custom function.
You would define your function and then call the callback function in it like this:
function myfunction(cb) {
cb(arg1, arg2);
}
Note, there are multiple methods of actually calling the callback function from within your custom function. If you just need to call it normally and don't care about the this argument, you can just use:
cb();
If you want to set the this argument to something, you can use this:
cb.call(thisArg, arg1, arg2);
If you want to pass along your current arguments or pass an array of arguments and set the this argument, you would use this:
cb.apply(thisArg, argArray);
References on .call() and .apply().
Your current code has a javascript error in this area:
test(rand_gyumolcs, link, callback){
callback();
};
This is not legal javascript. I don't know what you're trying to do, but this looks like half of a function declaration and half of a function call. If you just want to call the test function, you would just use this:
test(rand_gyumolcs, link, callback);
Inside of test, if you want the callback function to be called after the animation is complete, then you would have to hook the completion function of the animation and call the callback then.
completion function for the animation. Look at the doc for the jQuery animate function and you will see that the last argument is a callback function that will be called when the animation is complete. You need to provide that callback function to your gyum_mozgas2 function as an argument and then pass it to the .animate() call in that function. The animate() function will then call it when the animation completes.Here's an example with a callback with a return value that's also taking input parameters:
function test2(arg1, arg2, callback) {
var result = callback(arg1, arg2);
alert('arg1=' + arg1 + ', arg2=' + arg2 + ', result=' + result);
}
test2(1, 2, function(a, b) { return a + b; });
function myfunction(callback) {
// something
callback();
}
myfunction(callback);
notice I am not invoking the callback but just passing it as a function reference to my function. I then invoke it IN the function at the end or wherever you want to do it.
Here is another way you can use callback in javascript, this method ensures that you can safely execute a condition based on the result you get from call back.
// Function call.
validateCondition(function(isValid){
if(isValid) {
executeThisFunction();
} else {
// Do something else.
}
});
function validateCondition(callback) {
var isvalid = true;
// some calculation to check isValid.
callback(isValid);
}
