The answer
Because you use one listener on the parent instead of one per child. The closure captures the parent, not each child. For many children, this saves significant memory.
Callbacks and Event Listeners as Closures in JavaScript
Why does event delegation reduce closure-related memory usage in JavaScript?
More FAQs in Callbacks and Event Listeners as Closures in JavaScript
Yes. Every event listener closes over variables from where it was defined. This is how a click handler can access and update a count variable defined in the enclosing function.
Every callback is a closure. The callback function closes over variables from its defining scope. This is how setTimeout callbacks, map callbacks, and event handlers can access outer state when they run later.
Yes. If a listener closes over a DOM element and the element is removed from the DOM without removing the listener, the element stays in memory because the closure keeps a reference to it.
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