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I have this very basic calculator:

<html>
    <body>
        <form name="form">
            <input type="text" name="num1" />
            <input type="text" name="num2" />
            <input type="text" name="res" />
            <input type="button" value="+" onclick="form.res.value = form.num1.value + form.num2.value" />
        </form>
    </body>
</html>

But it treats form.num1.value and form.num2.value as string and because of it the result is the concatenation of these values instead of addition.

How to treat them as numbers?

I have this very basic calculator:

<html>
    <body>
        <form name="form">
            <input type="text" name="num1" />
            <input type="text" name="num2" />
            <input type="text" name="res" />
            <input type="button" value="+" onclick="form.res.value = form.num1.value + form.num2.value" />
        </form>
    </body>
</html>

But it treats form.num1.value and form.num2.value as string and because of it the result is the concatenation of these values instead of addition.

How to treat them as numbers?

  • javascript
  • html
Share Improve this question asked Dec 6, 2013 at 12:59 BillieBillie 9,14612 gold badges42 silver badges71 bronze badges
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4 Answers 4

Reset to default 6

Wrap each value in a parseInt(value, 10) or parseFloat(value).

Shortest way is the unary plus operator, which converts to Number:

+form.num1.value + +form.num2.value

Note: it will return NaN for mixed inputs like "10 potatoes". To avoid that, you can use parseInt or parseFloat.

Try to convert them to number like this:

onclick="Numberform.res.value = Number(form.num1.value) + Number(form.num2.value)"

Convert them to numbers with the + operator or parseFloat.

本文标签： javascriptHow to treat input field value as a numberStack Overflow

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