function getByClassName(obj,cls){
var elements=obj.getElementsByTagName('*');
var result=[];
for(var i=0;i<elements.length;i++){
if(elements[i].className==cls){
result.push(elements[i]);
}
}
return result;
}
function hasClass(obj,cls){
return obj.className.match(new RegExp("(\\s^)"+cls+"(\\s$)"));
}
function removeClass(obj,cls){
if(hasClass(obj,cls)){
var reg =new RegExp("(\\s^)"+cls+"(\\s$)");
obj.className=obj.className.replace(reg,"");
}
}
function addClass(obj,cls){
if(!hasClass(obj,cls)){
obj.className += " " +cls;
}
}
window.onload = function() {
window.onscroll = function() {
var top = document.documentElement ? document.documentElement.scrollTop : document.body.scrollTop;
var menus = document.getElementById('menu').getElementByTagName('a');
var items = getByClassName(document.getElementById('content', 'item'));
var currentId = '';
for(var i = 0; i<items.length; i++) {
var _item = items[i];
var _itemTop = _item.offsetTop;
if(top > _itemTop -200) {
currentId = _item.id;
} else {
break;
}
}
if(currentId) {
for(var j= 0; j < menus.length; j++) {
var _menu = menus[j];
var _href = _menu._href.split('#');
if (_href[_href.length - 1] != currentId) {
removeClass(_menu,'current');
} else {
addClass(_menu,'current');
}
}
}
};
};