想要通過不斷執(zhí)行定時器，改變元素的opacity,但是只函數(shù)每次獲取的元素的opacity都是0，沒有被累加；代碼如下：function appear() {   var opity = document.getElementById('fade-obj').style.opacity;     console.log(document.getElementById('fade-obj').style.opacity);        if(opity != 1) {           document.getElementById('fade-btn').disabled = 'true';                  opity += 0.2;        document.getElementById('fade-obj').style.opacity = opity;        setTimeout(appear,500);    }else{        document.getElementById('fade-btn').innerHTML = '淡出';        document.getElementById('fade-btn').removeAttribute('disabled');    }}document.getElementById('fade-btn').addEventListener('click', function() {      if (document.getElementById('fade-btn').innerHTML == '淡入') {        setTimeout(appear,500);    }}, false)結(jié)果如下：不知道為什么document.getElementById('fade-obj').style.opacity的值不變