延迟加载(lazy loading)
1 function addHandler(target, eventType, handler) { 2 if (target.addEventListener) { 3 addHandler = function(target, eventType, handler) { 4 target.addEventListener(eventType, handler, false); 5 }; 6 } else { 7 addHandler = function(target, eventType, handler) { 8 target.attachEvent("on" + eventType, handler); 9 }; 10 } 11 addHandler(target, eventType, handler); 12 } 13 14 function removeHandler(target, eventType, handler) { 15 if (target.removeEventListener) { 16 removeHandler = function(target, eventType, handler) { 17 target.removeEventListener(eventType, handler, false); 18 }; 19 } else { 20 removeHandler = function(target, eventType, handler) { 21 target.detachEvent("on" + eventType, handler); 22 }; 23 } 24 removeHandler(target, eventType, handler); 25 }
当一个函数在页面中不会被立刻调用时,延迟加载是最好的选择。