## 問題 Problem 你只想執行函數一次，把一系列的調用合并成一個單一的調用，在這一些列調用的開頭或者結尾執行。 You want to execute a function only once, coalescing multiple sequential calls into a single execution at the beginning or end. ## 方法 Solution 使用一個具名函數： With a named function: ~~~ debounce: (func, threshold, execAsap) -> timeout = null (args...) -> obj = this delayed = -> func.apply(obj, args) unless execAsap timeout = null if timeout clearTimeout(timeout) else if (execAsap) func.apply(obj, args) timeout = setTimeout delayed, threshold || 100 ~~~ ~~~ mouseMoveHandler: (e) -> @debounce((e) -> # Do something here, but only once 300 milliseconds after the mouse cursor stops. 300) someOtherHandler: (e) -> @debounce((e) -> # Do something here, but only once 250 milliseconds after initial execuction. 250, true) ~~~ ## 詳解 Discussion 參看John Hann的這篇很贊的文章[debouncing JavaScript methods](http://unscriptable.com/2009/03/20/debouncing-javascript-methods/)。 Learn about?[debouncing JavaScript methods](http://unscriptable.com/2009/03/20/debouncing-javascript-methods/)?at John Hann’s excellent blog article.