The JavaScript statement is executed in one row. However, for the preceding animation effect statement, the subsequent statement can be executed before the animation effect is completed, which may cause incorrect results. Therefore, the previous hide, show, fadeIn, fadeOut, slideIn, slideOut, and animation all support a callback optional parameter. You can add a callback function for these methods and call it after the animation is completed. The typical syntax is as follows: $ (selector ). hide (speed, callback); for example, in the following example, <p> hide and run: [javascript] $ ("button "). click (function () {$ ("p "). hide ("slow", function () {alert ("The paragraph is now hidden") ;}); $ ("button "). click (function () {$ ("p "). hide ("slow", function () {alert ("The paragraph is now hidden") ;}); The Alert in The following example is displayed before The hiding is complete. [Javascript] $ ("button "). click (function () {$ ("p "). hide (1000); alert ("The paragraph is now hidden") ;}); $ ("button "). click (function () {$ ("p "). hide (1000); alert ("The paragraph is now hidden ");});