How to get old Value with onchange() event in text box

user_198799 0
Viewed 266007

I have a text input. A value is populated into it when the page loads. If the user changes anything in text box, then I want to get the changed value (the new value) and old value. But calling ELEMENT.value it only returns the changed/new value.

How do I get the old value?

Here is my code:

      <head>
        <script type="text/javascript">
          function onChangeTest(changeVal) {
            alert("Value is " + changeVal.value);
          }
        </script>
      </head>
      <body>
        <form>
          <div>
              <input type="text" id="test" value ="ABS" onchange="onChangeTest(this)">  
          </div>
        </form>
      </body>
validation html javascript
9 Answers

You'll need to store the old value manually. You could store it a lot of different ways. You could use a javascript object to store values for each textbox, or you could use a hidden field (I wouldn't recommend it - too html heavy), or you could use an expando property on the textbox itself, like this:

<input type="text" onfocus="this.oldvalue = this.value;" onchange="onChangeTest(this);this.oldvalue = this.value;" />

Then your javascript function to handle the change looks like this:

    <script type="text/javascript">
    function onChangeTest(textbox) {
        alert("Value is " + textbox.value + "\n" + "Old Value is " + textbox.oldvalue);
    }
    </script>
user_2134740

element.defaultValue will give you the original value.

Please note that this only works on the initial value.

If you are needing this to persist the "old" value every time it changes, an expando property or similar method will meet your needs

user_88030

Maybe you can store the previous value of the textbox into a hidden textbox. Then you can get the first value from hidden and the last value from textbox itself. An alternative related to this, at onfocus event of your textbox set the value of your textbox to an hidden field and at onchange event read the previous value.

ScarletGarden_553510
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