window.onload = function(){ function $(id){ return document.getElementById(id); } $('btn').onclick = function(){ var that = this; that.disabled = true; var count = 5; var timer = setTimeout(fn,1000); function fn(){ count--; if(count>0){ that.innerHTML = "剩余时间"+ count +"s"; setTimeout(fn,1000); }else{ that.innerHTML ="重新发送短信"; that.disabled = false; } } } }