How to add numbers entered by user in Javascript
Question
The following is the JavaScript I did in order to try to add two numbers entered by the user but the result I'm getting is "NaN":
<HTML>
<HEAD>
<TITLE>JavaScript-Functions</TITLE>
</HEAD>
<BODY>
<H1>JavaScript-Functions</H1>
<P>This function will add two numbers.</P>
<script type="text/JavaScript">
<!-- This is a math function -->
var x = prompt("Please enter the first number: ");
var y = prompt("Please enter the second number: ");
function addTwo(x, y)
{
var xNum;
xNum = parseInt(x);
var yNum;
yNum = parseInt(y);
return xNum + yNum;
}
document.write(addTwo(x, y));
</script>
</BODY>
</HTML>
4 answers
solution1
1 2014-05-03 05:41:13
Everything looks good here, except the html comment
<!-- This is a math function -->
in script tag.
solution2
0 2014-05-03 05:40:58
如果您提供数字作为输入，则表示它一定可以工作，否则会抛出错误“ NaN”。
solution3
0 2014-05-03 05:52:51
try to use callback. This is due to the asynchronous evented I/O model of javascript.
var x = prompt("Please enter the first number: ");
var y = prompt("Please enter the second number: ");
function addTwo(x, y, callback){
var xNum;
xNum = parseInt(x);
var yNum;
yNum = parseInt(y);
var result = xNum + yNum;
callback(result);
}
addTwo(x, y, function(result){
document.write(result);
});
CODEPEN EDITED:link
solution4
0 2014-05-03 05:55:30
You could get rid of the parseInt() s and put a + in front of the prompt. That will parse the prompt response and change it from a string to an integer.
<script type="text/JavaScript">
<!-- This is a math function -->
var x = +prompt("Please enter the first number: ");
var y = +prompt("Please enter the second number: ");
document.write(x, y);
</script>
Just like that. So iv'e counted three things the + sign can do: 1. Concatenate strings and variables 2. It's like a parseInt() when placed in front of a window object 3. and its usual function, to add integers.
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