Javascript not adding two string numbers using parseInt function

Question

I have two < div > section having numbers inside. When number present in 1st < div > is clicked , 2nd content should show twice the value of 1st < div >.

I used following code but not working.

<div id="left"><a href="#" onclick="document.getElementById('right').innerHTML = (parseInt(document.getElementById('left').innerHTML) + parseInt(document.getElementById('left').innerHTML))">1</a></div>

<div id="right">1</div>

But the output is coming as

NaN

Can somebody help with correct code ? Thanks

If parseInt(x) is giving NaN then NaN + y is y + NaN is NaN. — Paul S.
– Paul S., Commented Jul 14, 2013 at 17:19
@logan I'm saying you're providing the wrong input, not using the wrong function. — Paul S.
– Paul S., Commented Jul 14, 2013 at 17:21

adeneo · Accepted Answer · 2013-07-14 17:25:33Z

2

The element #left contains the entire anchor, so you're getting all the HTML of the anchor back, and not just the number, which is why parseInt spits out NaN.

In other words:

document.getElementById('left').innerHTML

will return:

<a href="#" onclick="document.getElementById('right').innerHTML = (parseInt(document.getElementById('left').innerHTML) + parseInt(document.getElementById('left').innerHTML))">1</a>

And when parsing that as an integer it returns NaN ?

FIDDLE

You can solve it by doing:

<div id="left"><a href="#" onclick="calc(this); return false;">1</a></div>
<div id="right">1</div>

<script type="text/javascript">
    function calc(elem) {
        var val = parseInt(elem.innerHTML,10) * 2;
        document.getElementById('right').innerHTML = val;
    }
</script>

FIDDLE

edited Jul 14, 2013 at 17:25

answered Jul 14, 2013 at 17:19

adeneo

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3 Comments

Paul S. Over a year ago

You can parse it as an Integer, it just gives you NaN. Also, I'd suggest using .textContent over .innerHTML for this task.

adeneo Over a year ago

@PaulS. - well, yeah I suppose.

logan Over a year ago

@PaulS. .parseInt(document.getElementById('left').textContent is working fine... Thanks

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