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vamosrope14
14,932 PointsWhy couldn't we just put getJSON as a callback reference in the addEventListener method?
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2 Answers
highlandcow
7,352 PointsI actually got hung up on this question myself and couldn't come up with a good explanation other than "addEventListener expects a function declaration rather than a function invocation" which is either a gross oversimplification or plainly wrong (but conveniently gets me to the next video). Hoping someone in the community can chime in with a good explanation, perhaps with a simple example. Thanks!
Farid Lavizadeh
12,006 PointsUnless a named function is tied to an event, it will just run without the event occurring. Since getJSON(astrosUrl) is not tied to any event, it will run before a user clicks anything. To tie the named function to an event, a preceding anonymous function is used.
highlandcow
7,352 Pointshighlandcow
7,352 PointsI reviewed the "Callback Functions in JavaScript" course. Someone touched on this topic in the discussion on one of the videos: "When you put parentheses after a function name (with or without arguments), you are invoking ("calling") the function immediately and passing the function's return value as the argument. But for a callback, you want to pass the function itself, so it's important to not use the parentheses." Helped clear this up for me.