Question

js做一个简单的加减乘除计算，程序求改正

<input id="txt1" type="text" />
<select id="operator"> <option value="+">+</option>

<option value="-">-</option>

<option value="*">*</option>

<option value="/">/</option>
</select>

<input id="txt2" type="text" />
<input id="btn" type="button" value="=" onclick="return btn_onclick()" />
<input id="txt3" type="text" />

<script type="text/javascript">
function validate(str) {

var reg = /^\d+$/;

if (!reg.test(str)) {

alert("请输入数字");
}
}

function btn_onclick() {

var txt1 = document.getElementById("txt1").value;
var opra = document.getElementById("operator").value;
var txt2 = document.getElementById("txt2").value;
var btn = document.getElementById("btn").value;
var txt3 =0;

switch (opra) {
case "+":
txt3 = parseInt(txt1) + parseInt(txt2);
break;
case "-":
txt3 = parseInt(txt1) - parseInt(txt2);
break;
case "*":
txt4 = parseInt(txt1) * parseInt(txt2);
break;
case "/":
if (parseInt(txt2) != 0) {

txt3 = parseInt(txt1) / parseInt(txt2);
}
else {
alert("除数不能为0");
}
return;

default:

break;

}

document.getElementById(" txt3").value = txt3;
}

Answer 1

document.getElementById(" txt3").value = txt3;

多了和明个空格碰缺。。唤吵告。

document.getElementById("txt3").value = txt3;