js traversal delete array

$(function(){
    var aa = [1,1,2,3,3,4,4,5];
        
    alert(aa);
        
    for (var i = aa.length-1;i >= 0 ;i--) {
        if (aa[i] == 4) {
            aa.splice(i,1);        //执行后aa.length会减一
        }
    }
    
    alert(aa);
})