javascript 如何使用javascript动态获取输入值并执行算术运算
声明：本页面是StackOverFlow热门问题的中英对照翻译，遵循CC BY-SA 4.0协议，如果您需要使用它，必须同样遵循CC BY-SA许可，注明原文地址和作者信息，同时你必须将它归于原作者（不是我）：StackOverFlow
原文地址: http://stackoverflow.com/questions/20604138/
Warning: these are provided under cc-by-sa 4.0 license. You are free to use/share it, But you must attribute it to the original authors (not me):
StackOverFlow
How to get an input value dynamically and perform arithmetic operations using javascript
提问by Dinesh Kumar
I have created two input text fields by which the user have to give two values. Using javascript, I need to get those values perform addition, subtraction, multiplication and division based on the checkbox checked. How to do that?
我创建了两个输入文本字段，用户必须通过它们提供两个值。使用javascript，我需要根据选中的复选框让这些值执行加法、减法、乘法和除法。怎么做？
Here is my code..
这是我的代码..
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>JS Assignment</title>
<script>
function changeCheckBox() {
try {
var max = document.myform.check.length;
var count = 0;
for (var i = 0; i < max; i++) {
if (document.myform.check[i].checked == true) {
count++;
serNoChecked = i;
}
}
if (count == 1) {
for (var i = 0; i < max; i++) {
if (document.myform.check[i].checked == false) {
document.myform.check[i].disabled = true;
}
}
} else if (count == 0) {
for (var i = 0; i < max; i++) {
document.myform.check[i].disabled = false;
}
}
if (null == max) return false;
if (count == 0) {
return true;
} else if (count > 0) {
return false;
}
} catch (e) {
alert(e.message);
}
}
</script>
<script type="text/javascript">
function arith()
{
var number1 = document.getElementById('num1').value;
var number2 = document.getElementById('num2').value;
x=num1 + num2;
var demoP=document.getElementById("demo")
demoP.innerHTML="x=" + x;
}
</script>
</head>
<body background="photo.jpg" onload="arith()">
<h3>Simple JavaScript Arithmetic Operations</h3>
<form name="myform" method="get">
Value 1 <input type ="text" id="num1"> <br><br>
Value 2 <input type="text" id="num2"> <br><br>
<input type="checkbox" name="check" value="check1" id="check1" onclick="changeCheckBox()">Addition<br>
<input type="checkbox" name="check" value="check2" id="check2" onclick="changeCheckBox()">Subtraction<br>
<input type="checkbox" name="check" value="check3" id="check3" onclick="changeCheckBox()">Multiplication<br>
<input type="checkbox" name="check" value="check4" id="check4" onclick="changeCheckBox()">Division<br><br>
<input type="submit" value="Submit">
</form>
<p id="demo"></p>
</body>
</html>
回答by Sterling Archer
Try sending the value of the HTML into the function, and then use those as an if statement check (or switch statement).
尝试将 HTML 的值发送到函数中，然后将它们用作 if 语句检查（或 switch 语句）。
<form name="myform" method="get">
Value 1 <input type ="text" id="num1"> <br><br>
Value 2 <input type="text" id="num2"> <br><br>
<input type="checkbox" name="check" id="check1">Addition<br>
<input type="checkbox" name="check" id="check2">Subtraction<br>
<input type="checkbox" name="check" id="check3">Multiplication <br>
<input type="checkbox" name="check" id="check4">Division<br><br>
<input type="submit" value="Submit">
<p id="demo"></p>
Notice the valueattributes now have unique value. And you're sending that into the function as a parameter.
请注意，value属性现在具有唯一值。你将它作为参数发送到函数中。
Now just have a function that returns what you want
现在只要有一个函数返回你想要的
var newVal = "Unset";
var plus = document.getElementById("check1");
var minus = document.getElementById("check2");
var times = document.getElementById("check3");
var divide = document.getElementById("check4");
var demoP=document.getElementById("demo");
plus.onclick = function() {
var n1 = parseFloat(document.getElementById('num1').value);
var n2 = parseFloat(document.getElementById('num2').value);
newVal = n1+n2;
demoP.innerHTML="x=" + newVal;
}
minus.onclick = function() {
var n1 = parseFloat(document.getElementById('num1').value);
var n2 = parseFloat(document.getElementById('num2').value);
newVal = n1-n2;
demoP.innerHTML="x=" + newVal;
}
times.onclick = function() {
var n1 = parseFloat(document.getElementById('num1').value);
var n2 = parseFloat(document.getElementById('num2').value);
newVal = n1*n2;
demoP.innerHTML="x=" + newVal;
}
divide.onclick = function() {
var n1 = parseFloat(document.getElementById('num1').value);
var n2 = parseFloat(document.getElementById('num2').value);
newVal = n1/n2;
demoP.innerHTML="x=" + newVal;
}
