I'm having trouble understanding event listeners and what variables they send to the function they call.
For example, I added an event listener to this cell with the intention of calling a function which checks if the mouse is pressed down while moving over an element:
cell.addEventListener("mousemove", cellControl);
function cellControl(e) {
if (e.buttons == 1) {
// Do things
}
}
I was able to make this function work by finding other stack overflow answers but I don't understand why it works. The event listener calls cellControl
without passing any variables, but the function cellControl
receives an object anyways which I can check for data.
Why did the event listener send this data, and how can I find out what data different event listeners send to the functions I call? I read through this page but couldn't find the answer.
the callback accepts a single parameter: an object based on Event describing the event that has occurred
The parameter is a JavaScript Event Object. You can find the properties here https://developer.mozilla.org/en-US/docs/Web/API/Event#properties