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JavaScript

Posted by Trevor Johnson
Trevor Johnson
14,427 Points

JavaScript Calculator Bug!

Hey there, I am on a JavaScript calculator project, but I have run into an issue that I am struggling to resolve. I want my calculator to display at most 9 characters, including a ‘-’ and ‘.’, but my trouble is that whenever a minus or a dot is put into my string my function that cuts off the extra characters doesn’t work. Try pressing a button 9 times and you will see that it will cap itself and not overflow. Press the +/- button, or add a decimal in there and it will go on forever. switch it back to positive and it cuts off. I have spent a while on this and I haven’t had any luck. I appreciate the feedback and if you notice anywhere else my code can improve please let me know.

Give a search for this and you will see all the places I am trying to run the function: $('#total').html(checkLength(number));

https://codepen.io/tsjohns9/pen/rzOypK?editors=1111

Ivan Penchev
Ivan Penchev
13,833 Points

Including your code will greatly increase the chances, we as a community, to help you.

Trevor Johnson
Trevor Johnson
14,427 Points

Whoops, its in there now

1 Answer

Steven Parker
Steven Parker
243,657 Points
Steven Parker
Steven Parker
243,657 Points

Function checkLength was checking the value of num itself instead of its length:

//Checks if number is longer than 9 
  function checkLength(num) {
    if (num.length > 9) {           // <- was originally "num > 9"
      return num.substr(0, 9);
    }
    return num;
  }

But it does seem a bit odd that converting a number to negative would also divide it by 10!

Trevor Johnson
Trevor Johnson
14,427 Points

You are awesome

Trevor Johnson
Trevor Johnson
14,427 Points

I have a question for you though Steven now that you fixed that problem. What is the best way to cleanly add decimal numbers because it doesn't seem to consistently add up the right way. And, my Math.abs method to switch between positive and negative rounds my decimals which I don't want either.

Steven Parker
Steven Parker
243,657 Points
Steven Parker
Steven Parker
243,657 Points

It's not Math.abs but using parseInt to convert the string that truncates the decimals. Use parseFloat instead.

I'm not sure what you mean by "doesn't seem to consistently add up the right way" — can you give some specific examples?

Trevor Johnson
Trevor Johnson
14,427 Points

Try adding two decimals together like .1 + .2 and you get .3000000. Or .78 - 3 and you get -2.219999

Trevor Johnson
Trevor Johnson
14,427 Points

When does converting a number to negative divide it by 10? I haven't come across that.