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26,050 PointsIs "callback" a keyword? Not as a parameter, but as part of the function's body?
Hi, I thought callbacks were simply functions passed as arguments, but this lesson's format is more advanced than that. At least I find it harder to grasp. When writing "callback" in the parameters, that makes sense to me as a place for an argument. However, what about in the function's body. My apologies if this is not clear.
Best,
Matt
1 Answer
Brendan Whiting
Front End Web Development Techdegree Graduate 84,738 Pointscallback
is not a keyword, and you're on the right track here. In this example, callback
is the name of a parameter where a function will be passed in. Then, in the body of the function, we call the function that was passed in to the callback parameter. We can call it whatever we want.
function add(a, b, fancyFunc) {
fancyFunc(a + b);
}
add(2, 4, function(sum) {
console.log(sum); // 6
});
I renamed it fancyFunc
and it still works. In this case, we're passing an anonymous function as the argument for fancyFunc
. But we could also have passed in a function that has a name.
function add(a, b, fancyFunc) {
fancyFunc(a + b);
}
function myLogger(val) {
console.log(val);
}
add(2, 4, myLogger);
I'm declaring a function named myLogger
. Then, I'm passing that function in as the 3rd argument to the add
function. So myLogger
is now in the fancyFunc
parameter. In the body of add
, it's going to call whatever function is passed in. So by calling fancyFunc
it ends up calling myLogger
.
Let me know if you have more questions.