something wrong with my loop?

I want to make a box disappear and reappear alternatively by using the loop. The problem is that the box does not appear at all though the loop runs until i=10. Can someone explain this?

    for(var i=0;i<10;i++){
        if(document.getElementById("box").style.display=="none"){
            document.getElementById("box").style.display="block";}
        else{
            document.getElementById("box").style.display="none";
        }
        console.log(i);
    }