带 Switch 的简单 JavaScript 计算器
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Simple javascript calculator with Switch
提问by MoeSzislak
I need some help with a simple calculator I am doing with javascript.
我需要一些关于我正在使用 javascript 的简单计算器的帮助。
The js code is as follows (my teacher want's me to use 4 functions, for each kind of operation):
js代码如下（老师要我用4个函数，每种操作）：
<script>
function plus(a,b) {
return (a + b);
}
function minus(a,b) {
return (a - b);
}
function multiply(a,b) {
return (a * b);
}
function divide(a,b) {
return (a / b);
}
function calc() {
var x = document.getElementById("oper1").value;
var y = document.getElementById("operx").value;
var z = document.getElementById("oper2").value;
var w = document.getElementById("resul").value;
switch (y) {
case '0':
w = plus(x, z);
break;
case '1':
w = minus(x, z);
break;
case '2':
w = multiply(x, z);
break;
case '3':
w = divide(x, z);
break;
default:
w = "Don't really know..";
}
}
</script>
<input type="text" id="oper1" value="">
<select id="operx">
<option value="0">SUMAR</option>
<option value="1">RESTAR</option>
<option value="2">MULTIPLICAR</option>
<option value="3">DIVIDIR</option>
</select>
<input type="text" id="oper2" value="">
<input type="button" onClick="calc();" value="=">
<input type="text" id="resul" value="">
My code isn't working, in fact is not responding anything and I don't see any errors so I can debug... could anyone tell me if you see my mistake here? I've tried hundreds of combinations but without having an debug console or something.
我的代码不起作用，实际上没有任何响应，我没有看到任何错误，所以我可以调试......如果你在这里看到我的错误，有人能告诉我吗？我已经尝试了数百种组合，但没有调试控制台或其他东西。
采纳答案by Sirko
JavaScript does not use pointers in the way you intend to use them. You have to explicitly write back your result to the output field:
JavaScript 不会以您打算使用它们的方式使用指针。您必须明确地将结果写回输出字段：
function calc(){
// most of your stuff
// just replace the var w = document ... line with just
var w;
// your other code
document.getElementById("resul").value = w;
}
Furthermore, you should parse the input values into a number using either parseInt()or parseFloat(). If you don't JavaScript will treat the input values as strings and then interprets +as string concatenation, for example.
此外，您应该使用parseInt()或将输入值解析为数字parseFloat()。例如，如果您不这样做，JavaScript 会将输入值视为字符串，然后解释+为字符串连接。
回答by David Starkey
var w = document.getElementById("resul").value;
This does not allow you to set W and then have the <input/>update itself. You could do one of the following instead.
这不允许您设置 W 然后<input/>自行更新。您可以改为执行以下操作之一。
After setting wdo document.getElementById("resul").value=w;
设置后w做document.getElementById("resul").value=w;
OR
或者
var w = document.getElementById("resul");
w.value=etc.
Also, bonus points if you validate your form (nice function for this case is IsNumeric())
此外，如果您验证您的表单，则可以获得奖励积分（这种情况下的好功能是IsNumeric()）
回答by Noel Moses Mwadende
Your program should look like this
你的程序应该是这样的
<script>
function plus(a,b) {
return (a + b);
}
function minus(a,b) {
return (a - b);
}
function multiply(a,b) {
return (a * b);
}
function divide(a,b) {
return (a / b);
}
function calc() {
var w;
var x = document.getElementById("oper1").value;
var y = document.getElementById("operx").value;
var z = document.getElementById("oper2").value;
//document.getElementById("resul").innerHTML=w;
switch (y) {
case '0':
w = plus(x, z);
document.getElementById("resul").innerHTML=w;
break;
case '1':
w = minus(x, z);
document.getElementById("resul").innerHTML=w;
break;
case '2':
w = multiply(x, z);
document.getElementById("resul").innerHTML=w;
break;
case '3':
w = divide(x, z);
document.getElementById("resul").innerHTML=w;
break;
default:
w = "Don't really know..";
}
}
</script>
<input type="text" id="oper1" value="">
<select id="operx">
<option value="0">SUMAR</option>
<option value="1">RESTAR</option>
<option value="2">MULTIPLICAR</option>
<option value="3">DIVIDIR</option>
</select>
<input type="text" id="oper2" value="">
<input type="button" onClick="calc();" value="Solve"><br/><br/>
<p id="resul">The answer is : </p>