Trying to use javascript to change the weight of a product error [object HTMLSpanElement]

Question

Hey guys i'm wondering if you could help me figure out this problem ive been having. im trying to get the weight of a product to add or subtract itself whenever a plus or minus button is clicked on.

I've established my weight from the database and set an id to that weight. then in javascript I've used getElementByid and added my weight id like so:

 <span id="weight"><?php echo ( $value['weight'] );  ?></span> kg<br/>
    <button onclick="minus()"> - </button><span id="quantity"> 1 </span><button onclick="plus()"> + </button><br/>  

<script>

function plus(){

    // parseint changes strings into intergers 

    document.getElementById('weight').innerHTML = parseInt( document.getElementById('weight').innerHTML) +weight;

}
function minus(){

    document.getElementById('weight').innerHTML = parseInt( document.getElementById('weight').innerHTML) -weight;

}

<script>

when i go onto the front end and press the add or minus button theres a message that comes up [object HTMLSpanElement] kg. just wondering what i did wrong here?

You haven't defined the `weight` variable. [Right now it refers to the `` element](https://stackoverflow.com/questions/3434278/do-dom-tree-elements-with-ids-become-global-variables). — Ivar, Jun 16 '21 at 09:11
I doubt the message would come up like that if you press the minus button ... minus would result in `NaN` .. .also, plus would result in `1[object HTMLSpanElement]` - not just `[object HTMLSpanElement]` — Jaromanda X, Jun 16 '21 at 09:16
so would the variable be like : var weight = document.getElementById('weight').innerHTML; — ashley gibson, Jun 16 '21 at 09:17
you could also put `var weight = ` as the first line of your script — Jaromanda X, Jun 16 '21 at 09:21
the +weight.textContent just keeps adding the same number e.g 34kg becomes 3434kg — ashley gibson, Jun 16 '21 at 09:22
@KrystianSztadhaus - or `let` - depending if `weight` should be modifiable :p - of courswe — Jaromanda X, Jun 16 '21 at 09:23
You are already using `document.getElementById('weight')` to get the weight on the left hand side of the expression. Do you really want to use the same value on the right and side? This means that you are doubling the value with `+` and setting the value to `0` with `-`. — Ivar, Jun 16 '21 at 09:23
Ya know what, you guys are just incredible. thank you so much its worked!! — ashley gibson, Jun 16 '21 at 09:26
Odd, since the `kg` isn't anywhere in that span, or in the code ... the only kg should be after the weight span — Jaromanda X, Jun 16 '21 at 09:26
its just after the span kg
but yeah thank you so much guys. means a lot — ashley gibson, Jun 16 '21 at 09:32

Trying to use javascript to change the weight of a product error [object HTMLSpanElement]

0 Answers0