javascript onblur onMouseOver计算税和自动填充表单输入

Question

After 2 days searching I give up. I have a form and need to add (autofill) taxes to the input total price but in a easy simple way:

<form name="form" action="go.php">

<input name="cost" type="text">

<input name="costplustax" type="text" value=" here we autofill cost +19%>

<input type="submit" value="ready to mysql">

I can nothing about javascript tested a lot of examples but all complicated. I just need to autofill the input costplustax with cost plus tax

example

cost 100.000 because tax is 19% then we autofilll the input with onblur or onMouseOver to 119.000

How to do this?

Answer 1

First add an ID to your elements (this makes referencing the elements with JS easier). Ex

<input name="cost" type="text">

becomes

<input name="cost" ID="cost" type="text">

You need to add a script tag to house the JS code like this

<script>
  var taxPerc = .19; 
  document.getElementById("cost").onblur = function(){
    document.getElementById("costplustax").value = parseFloat(document.getElementById("cost").value) * (1.00 + taxPerc)
  }
</script>