问下script放在body里面和放在下面的区别？
如果要是像老师那样把script放在下面的话，程序顺利执行。
但是想把script放在head里面用window.onload的话，程序就报错说ScrollUp没有定义，如下面的代码：
window.onload=function(){
var area = document.getElementById('moocBox'),
con1 = document.getElementById('con1'),
con2 = document.getElementById('con2');
var time = 10;
con2.innerHTML = con1.innerHTML;
var timer = null;
area.onmouseover=function(){
timer=setInterval('scrollUp()',time);
}
area.onmouseout=function(){
clearInterval(timer);
}
function scrollUp(){
if (area.scrollTop >= con1.offsetHeight) {
area.scrollTop = 0;
} else {
area.scrollTop++;
}
}
}但是如果把scrollUp写在window.onload外面就可以了，像下面这样：
window.onload = function() {
var area = document.getElementById('moocBox'),
con1 = document.getElementById('con1'),
con2 = document.getElementById('con2');
var time = 10;
con2.innerHTML = con1.innerHTML;
var timer = null;
area.onmouseover = function() {
timer = setInterval('scrollUp()', time);
}
area.onmouseout = function() {
clearInterval(timer);
}
}
function scrollUp() {
var area = document.getElementById('moocBox'),
con1 = document.getElementById('con1'),
con2 = document.getElementById('con2');
if (area.scrollTop >= con1.offsetHeight) {
area.scrollTop = 0;
} else {
area.scrollTop++;
}
}这是为什么?
