assign multiple same callback function for event with possible performance issue?

Question

i have question in my head. if i run the following code.

function test() { console.log('test'); }
event.addEventListner('click', test);
event.addEventListner('click', test); 
event.addEventListner('click', test);

i guess the event callback will be overlay each other and result console.log('test') once, but what happened to those extra event listeners? do they get garbage collected and removed from memory? will it lead to memory leak if mutiple event been assigned with same function?

many thanks

Quentin · Accepted Answer · 2019-03-10 00:33:07Z

2

what happened to those extra event listeners?

See the MDN documentation:

If multiple identical EventListeners are registered on the same EventTarget with the same parameters, the duplicate instances are discarded. They do not cause the EventListener to be called twice, and they do not need to be removed manually with the removeEventListener() method.

do they get garbage collected and removed from memory?

They never exist in the first place.

answered Mar 10, 2019 at 0:33

Quentin

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