<input type="text" id="num1" value="" />
<select id="mySelect">
<option value="+">+</option>
<option value="-">-</option>
<option value="*">*</option>
<option value="/">/</option>
</select>
<input type="text" id="num2" value="" />
<input type="button" id="jisuan" value="计算" />
//js
<script>
var oTxt1 = document.getElementById('num1')
var oTxt2 = document.getElementById('num2')
var oSelect = document.getElementById('mySelect')
var oBtn = document.getElementById('jisuan')
oBtn.onclick=function(){
switch(oSelect.value){
case '+':
alert(parseInt(oTxt1.value)+parseInt(oTxt2.value))
break
case '-':
alert(parseInt(oTxt1.value)-parseInt(oTxt2.value))
break
case '*':
alert(parseInt(oTxt1.value)*parseInt(oTxt2.value))
break
case '/':
if(parseInt(oTxt2.value) !== 0){
alert(parseInt(oTxt1.value)/parseInt(oTxt2.value))
}else{
alert('除数不能为0')
}
break
default:
alert('Bug!!!')
}
}
</script>
<!DOCTYPE html><html>
<head>
<meta http-equiv="Content-Type" content="text/htmlcharset=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>
function test(){var txt1 = document.getElementById("txt1"),
txt2 = document.getElementById("txt2"),
txt3 = document.getElementById("txt3"),
opt = document.getElementById("sel")
txt3.value = eval(txt1.value + opt.value + txt2.value)//eval函数可计算某个字符串，并执行其中的的js代码
} <input type="text" id="txt1" />
<select id="sel">
<option value="+">+</option>
<option value="-">-</option>
<option value="*">*</option>
<option value="/">/</option>
</select>
<input type="text" id="txt2" />
=
<input type="text" id="txt3" />
<input type="button" id="btn" value="计算" onclick="test()"/>
