//显示数字的ID为 num
//加号添加onclick事件 onclick=addNum()
<script>
function subNum(){
document.getElementById("num").value=document.getElementById("num").value-1
}
function addNum(){
document.getElementById("num").value=document.getElementById("num").value+1
}
</script>
<input class="input3 bor-e3 ml-8" id="reduce" type="button" value="-"><input class="input2 text-c" id="num" type="text" value="1">
<input class="input4 bor-e3" id="add" type="button" value="+">
<!--样式自己写--> var i = $("#num").val()
$("#add").click(function () {
i++
$("#num").attr("value", i)
}),
$("#reduce").click(function (){
i--
$("#num").attr("value", i)
if (i < 0) {
$("#num").attr("value", 0)
i = 0
}
})
//jQuery实现的，需要自己去下载jQuery文件
<!DOCTYPE html><html>
<head>
<meta http-equiv="Content-Type" content="text/html charset=utf-8" />
<title></title>
</head>
<body>
<table>
<tr>
<td><input type="button" value="add" onclick="setOp('+', 'add')"/></td>
<td><input type="button" value="miner" onclick="setOp('-', 'miner')"/></td>
<td><input type="button" value="times" onclick="setOp('*', 'times')"/></td>
<td><input type="button" value="divide" onclick="setOp('/', 'divide')"/></td>
</tr>
</table>
<table id="tb_calc" style="display:none">
<tr>
<td> <input id="x" type="text" style="width:100px" value="" name="x" /></td>
<td> <lable id="op" name="op"></lable> </td>
<td> <input id="y" type="text" style="width:100px" value="" name="y" /> </td>
<td> <input id="opTips" type="button" value="" onclick="calc()"/> </td>
<td> <lable id="z" name="z"></lable> </td>
</tr>
</table>
<script type="application/javascript">
function setOp(op, opTips)
{
var tb=document.getElementById("tb_calc")
tb.style.display = "none"
document.getElementById("x").value = ""
document.getElementById("y").value = ""
document.getElementById("z").innerText = ""
document.getElementById("op").innerText = op
document.getElementById("opTips").value = opTips
tb.style.display = "block"
}
function calc()
{
var x = parseInt(document.getElementById("x").value)
var y = parseInt(document.getElementById("y").value)
var op = document.getElementById("op").innerText
var z = ""
switch(op)
{
case '+':
z = x + y
break
case '-':
z = x - y
break
case '*':
z = x * y
break
case '/':
z = x / y
break
default:
z = ''
}
console.log(x, op, y, '=', z)
document.getElementById("z").innerText = z
}
</script>
</body>
</html>
实现的步骤，第一步是加4个按钮，如图所示：
第二步需要加两个输入框，两个，一个按钮
