title: How I can create a javascript and html sales tax calculator?
body: <p>Ok my problem is, I want to create a sales tax calculator. When the user, put the price of a item ( example a ball that cost 7 dollars) calculate their final price with the tax of 12%. </p>
  
  <p>But.. not just that, I want, if the user pick some item ( ball: $7, toy $4 and candy $2.. = $13) sum that item and add the sales tax ( $13 + 12%).</p>
  
  <p>in my code I have the basic   structure dont worry for that. </p>
  
  <p>Below i the code that i wrote, and dont works. I use HTML and Javascript.</p>
  
  <p>Please help me. </p>
  
  <p><div class="snippet" data-lang="js" data-hide="false" data-console="true" data-babel="false">
  <div class="snippet-code">
  <pre class="snippet-code-js lang-js prettyprint-override"><code>function CalculateIVU() {
    var price = document.forms.txts.value;
    var evaluation = price;
    var tax = 0.12 * evaluation;
    var final = +tax + +evaluation;
    document.getElementById('res').value = final;
  }</code></pre>
  <pre class="snippet-code-html lang-html prettyprint-override"><code>&lt;form name="forms" id="forma"&gt;
    &lt;table&gt;
      &lt;tr&gt;
        &lt;td&gt;
          &lt;label&gt;enter the value&lt;/label&gt;
          &lt;input type="text" name="txts" size=20&gt;
          &lt;/br&gt;
          &lt;label&gt;the tax is&lt;/label&gt;
          &lt;input type="text" name="resul" id="res"&gt;
        &lt;/td&gt;
      &lt;/tr&gt;
      &lt;tr&gt;
        &lt;td&gt;
          &lt;INPUT TYPE="button" NAME="one" VALUE="  1  " OnClick="forms.txts.value += '1'"&gt;
          &lt;INPUT TYPE="button" NAME="two" VALUE="  2  " OnCLick="forms.txts.value += '2'"&gt;
          &lt;INPUT TYPE="button" NAME="three" VALUE="  3  " OnClick="forms.txts.value  += '3'"&gt;
          &lt;INPUT TYPE="button" NAME="plus" VALUE="  +  " OnClick="forms.txts.value += '+ '"&gt;
          &lt;br&gt;
          &lt;INPUT TYPE="button" NAME="four" VALUE="  4  " OnClick="forms.txts.value += '4'"&gt;
          &lt;INPUT TYPE="button" NAME="five" VALUE="  5  " OnCLick="forms.txts.value += '5'"&gt;
          &lt;INPUT TYPE="button" NAME="six" VALUE="  6  " OnClick="forms.txts.value += '6'"&gt;
  
          &lt;br&gt;
          &lt;INPUT TYPE="button" NAME="seven" VALUE="  7  " OnClick="forms.txts.value+= '7'"&gt;
          &lt;INPUT TYPE="button" NAME="eight" VALUE="  8  " OnCLick="forms.txts.value += '8'"&gt;
          &lt;INPUT TYPE="button" NAME="nine" VALUE="  9  " OnClick="forms.txts.value += '9'"&gt;
  
          &lt;br&gt;
          &lt;INPUT TYPE="button" NAME="clear" VALUE="  c  " OnClick="forms.txts.value = ''" OnClick="forms.resul.value = ''"&gt;
          &lt;INPUT TYPE="button" NAME="zero" VALUE="  0  " OnClick="forms.txts.value += '0'"&gt;
          &lt;INPUT TYPE="button" NAME="DoIt" VALUE="  =  " OnClick="CalculateIVU() = eval(forms.txts.value);"&gt;
  
          &lt;br&gt;
          &lt;input type="button" id="input" value="Calcular" onClick='CalculateIVU();'&gt;
  
        &lt;/td&gt;
      &lt;/tr&gt;
  
  &lt;/form&gt;
  &lt;/div&gt;</code></pre>
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