javascript calculator: plus sign alternatives

Question

As I was researching my current question this article seemed to be promising but I could not figure out for myself if it was the answer to my question. So if anyone could help my that would be terrific.

This is my Function:

function CalculateIMSUB(form) {
  var Atext = form.input_1.value;
  var Btext = form.input_2.value;
  var val = form.val.value;
  var A = eval(Atext);
  var B = eval(Btext);
  if (isNaN(A)) A = 0;
  if (isNaN(B)) B = 0;
  var answer = A - B;
  form.Answer.value = answer;
}

This is my html:

<form>
  <INPUT TYPE=TEXT name="input_1" SIZE=15>
  <INPUT TYPE=TEXT name="input_2" SIZE=10>
  <INPUT TYPE="button" VALUE="+" name="SubtractButton"
  onclick="CalculateIMSUB(this.form)">
  <INPUT TYPE=TEXT NAME="Answer" SIZE=12>
  <input type="hidden" name="val" value="" />
</form>

My question:

Can I add with "/"

For instance currently, if you were to type 10 / 5 in the input 1 text field and click calculate you would have an answer of 2 in the Answer text field. Since as we all know 10 divided by 5 equals 2. I would like to be able to type 10/5 into the input 1 text field and receive an answer of 15 which would be the equivalent to 10+5. Your help is greatly appreciated, thank you and here is my jsFiddle.

and why is the plus sign there when you're subtracting the numbers?...not sure about overloading the operators, but you could do what you want with a regex — גלעד ברקן, Feb 21 '13 at 05:13
@Blender the reason I would like to do that is this is for inventory at my work. We use the division sign to represent a different location when we are using pen and paper. — Clint, Feb 21 '13 at 05:26
@groovy, the plus sign is there because in my function. You add everything from the input1 (5+5+5) field and subtract it by everything from the input 2 (2+2+2) field. which would give a result from the numbers I provided in the parenthesis to be 15-6 which is 9 — Clint, Feb 21 '13 at 05:29

elclanrs · Answer 1 · 2013-02-21T05:29:56.893

1

Here's a very simple calculator implementation with prototypes and a module, no eval needed.

var calc = (function calcModule() {
  function Calculator(operation) {
    this.op = operation;
    this._init();
  }

  Calculator.prototype = {
    _init: function() {
      this.n1 = +this.op.split(/\D/)[0];
      this.n2 = +this.op.split(/\D/)[1];
      this.result = this[this.op.match(/\D/)[0]]();
    },
    '+': function() { return this.n1 + this.n2 },
    '-': function() { return this.n1 - this.n2 },
    '*': function() { return this.n1 * this.n2 },
    '/': function() { return this.n1 / this.n2 }
  };

  return function(op) {
    return new Calculator(op);
  };
}());

You can change what the symbols do if you want to. You use it like so:

console.log(calc('20-15').result); //=> 5
console.log(calc('15/5').result); //=> 3
...

Note that it's very simple, it'll only work with two numbers, but just so you get an idea...

edited Feb 21 '13 at 05:29

answered Feb 21 '13 at 05:24

elclanrs

92,861
21
134
171

Thank you for the answer. But I would imagine it would be impractical for my [website](http://strubeinventory.info/home1.html). – Clint Feb 21 '13 at 06:10
`eval` will be even more impractical. A user could enter malicious code into any of those inputs... My example is very simple but with a bit of work you can use multiple numbers, plus this is more portable. – elclanrs Feb 21 '13 at 06:13
@Clint: Wanna crash your app in just a second? Enter `while(true)` into any input that it's being evaled and click "Master Calculation". BAAANG! That's why `eval` shouldn't be used for this. – elclanrs Feb 21 '13 at 06:21
You bring up a very good point. The website I provided is one I use with my tablet to enter inventory at my workplace. I provided the website as an example, I will shortly restrict access to the webpage so that only I can view and or submit forms. I am not a pro by any means so, I ask you if only I am using this would implementing your strategy be a sensible thing to do if I were the only one submitting data. That was what I meant when I said impractical – Clint Feb 21 '13 at 06:33

גלעד ברקן · Accepted Answer · 2013-02-21T06:07:08.060

0

You could also do this:

var Atext = form.first.value.replace(/\//g,"+");
var Btext = form.second.value.replace(/\//g,"+");

Which would replace all division operators behind the scenes so that your eval will process them as addition. (So you could put 5/5/5 and get 15, or what have you.)

edited Feb 21 '13 at 06:07

answered Feb 21 '13 at 05:56

גלעד ברקן

23,602
3
25
61

groovy, I believe you just became my new favorite person. Thank you – Clint Feb 21 '13 at 06:08

javascript calculator: plus sign alternatives

2 Answers2

Linked