Javascript 如何对输入标签中的两个数字求和？
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how to sum two numbers from input tag?
提问by user1599289
Possible Duplicate:
How to add two strings as if they were numbers?
可能的重复：
如何将两个字符串相加，就好像它们是数字一样？
I wrote a simple JavaScript code and I want to use two input box and add numbers from the two value. Here's the code, and I see the result 1520 instead of 35.
我写了一个简单的 JavaScript 代码，我想使用两个输入框并从两个值中添加数字。这是代码，我看到结果是 1520 而不是 35。
How can I fix it?
我该如何解决？
n1 <input type = "number" id = "n1" value=15 />
n2 <input type = "number" id = "n2" value=20 />
<p>Sum?</p>
<button onclick="sum()">Try it</button>
<p id="demo2">Result?? </p>
<script type="text/javascript">
function sum()
{
var fn, ln;
fn = document.getElementById("n1").value;
ln = document.getElementById("n2").value;
result = (fn+ln);
document.getElementById("demo2").innerHTML = result;
}
</script>
回答by David says reinstate Monica
Use parseInt(), or parseFloat(); the problem you were experiencing is that you were concatenating two strings, not adding two numbers. parseInt()(assuming that it finds a real number) addresses that issue by converting the string to a number:
使用parseInt(), 或parseFloat(); 您遇到的问题是您正在连接两个字符串，而不是将两个数字相加。parseInt()（假设它找到一个实数）通过将字符串转换为数字来解决该问题：
function sum()
{
var fn, ln, result;
fn = parseInt(document.getElementById("n1").value, 10);
ln = parseInt(document.getElementById("n2").value, 10);
result = (fn+ln);
document.getElementById("demo2").innerHTML = result;
}
The , 10that appears after the valueis the radix, which ensures which number-base the returned number (if any) will be.
在, 10那之后的出现value是基数，这确保其中数个碱基返回的数字（如果有的话）会。
Also note that the resultvariable should be declared within the function as well, to avoid polluting the global scope (and possibly creating problems with other variables elsewhere).
另请注意，该result变量也应在函数内声明，以避免污染全局范围（并可能在其他地方与其他变量产生问题）。
References:
参考：
回答by KingKongFrog
result = (parseFloat(fn)+parseFloat(ln));
