为什么觉得闪的节奏有点不对了

         var oDiv = document.getElementById('text');
         var init = 0;
            setInterval(function () {
                if (init === 0){
                    oDiv.innerHTML = '☆☆☆今日特卖☆☆☆';
                    init = 1;
                }else {
                    oDiv.innerHTML = '★★★今日特卖★★★';
                    init = 0;
                }
            },500)