**
html代码 <input type="button" value="-" id="jian" > <input type="text" value="1" id="txt"> <input type="button" value="+" id="jia">
js代码 `var add=document.getElementById(“jia”);//获取值为+的按钮 add.οnclick=function(){//给+添加点击事件 var num=parseInt(document.getElementById(“txt”).value);//将文本框的值转化为数字 if (num<100){ document.getElementById(“txt”).value=num+1; } } var jian=document.getElementById(“jian”); jian.οnclick=function(){ var num=document.getElementById(“txt”).value; if (num!=1){ document.getElementById(“txt”).value=num-1; } }``
