                        課程
                    
                        /前端開發
                        
                            /JavaScript
                        
                        /焦點圖輪播特效

這個判斷把我搞暈了

function?animate?(offset)?{????
if?(offset?==?0)?{????
????return;????
}????
animated?=?true;????
var?time?=?300;????
var?inteval?=?10;????
var?speed?=?offset/(time/inteval);????
var?left?=?parseInt(list.style.left)?+?offset;?????
var?go?=?function?(){????
????if?(?(speed?>?0?&&?parseInt(list.style.left)?<?left)?||?(speed?<?0?&&?parseInt(list.style.left)?>?left))?{????
????????list.style.left?=?parseInt(list.style.left)?+?speed?+?'px';????
????????setTimeout(go,?inteval);????
????}else?{????
????????list.style.left?=?left?+?'px';????
????????if(left>-200){????
????????????list.style.left?=?-600?*?len?+?'px';????
????????}????
????????if(left<(-600?*?len))?{????
????????list.style.left?=?'-600px';????
????????}???????
????}????
}????
go();}

這是這節課下載來的代碼，我怎么覺得if里的(speed > 0 && parseInt(list.style.left) < left) || (speed < 0 && parseInt(list.style.left) > left) 一直都是成立的怎么else跳出去的？

圖片在第一個時parseInt(list.style.left)=-600，向左移animate(600); parseInt(list.style.left)<left = 0；滿足條件，

圖片在最后一個時parseInt(list.style.left)=-3000，向右animate(-600);parseInt(list.style.left)> left = -3600；也滿足條件，什么情況下跳出這個判斷條件？