外部関数に変数があり、その変数を変更する内部関数がある場合、なぜその変数は元の値に戻るのですか?
// Check which type of event registration browser supports
function addEvent(eventTarget, eventType, eventHandler){
if (window.addEventListener){
eventTarget.addEventListener(eventType, eventHandler);
}
else if (window.attachEvent){
var eventType = "on" + eventType;
eventTarget.attachEvent(eventType, eventHandler);
}
}
// Check if browser supports DOMContentLoaded
var DOMContentLoadedSupported = "no";
addEvent(document, "DOMContentLoaded", function(){
DOMContentLoadedSupported = "yes";
})
alert(DOMContentLoadedSupported) // alerts "no" not "yes". Why??