javascript - Addition operation issues?

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javascript - Addition operation issues?

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

javascript - Addition operation issues?

Hi i'm trying to do simple addition of two numbers in javascript. When i'm trying to get the two input element values, the result is coming in a concatenation of two numbers

Here is the code:

<html>
<title>
</title>
<head>
<script type="text/javascript">
function loggedUser() {
    //Get GUID of logged user
   //alert('success');
   var x, y , result;
   x = document.getElementById('value1').value;
   y = document.getElementById('value2').value;
   result=x+y;
   alert(result);
   document.getElementById('res').value = result;
}
</script>
</head>
<body>
<input type="text" id="value1"><br>
<input type="text" id="value2"><br>
<input type="text" id="res">
<input type="submit" value ="submit" onclick=loggedUser();>
</body>
</html>

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1 Answer

深蓝 · Answer 1 · 2021-10-23T18:42:29+0000

The "+" operator is overloaded. If any of the parameters is a string, they are all converted to strings and concatenated. If the parameters are numbers, then addition is done. Form control values are always strings.

Convert the parameters to numbers first using one of the following:

x = Number(document.getElementById('value1').value);

or

x = parseInt(document.getElementById('value1').value, 10);

or

x = parsefloat(document.getElementById('value1').value);

or

x = +document.getElementById('value1').value;

or

x = document.getElementById('value1').value * 1;

and so on...

Oh, you can also convert it only when necessary:

result = Number(x) + Number(y);

etc.

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