How do I return last valid input when a validating a text field using Javascript call inside a Rails helper?

Question

I have a text field

text_field_tag('version',version, :cols => 20 , :onchange => "validateVer(this);")

In validateVer java script function I am checking whether a valid float is entered, if not I am returning by default 1.0. How can I return the previous value in text field(version).

Answer 1

One way to do this is to store the last valid value in a data- attribute:

// modify your validateVer function to return false if validation fails and true otherwise
function validateVer(elem) {
}

function changeIfValid(elem) {
  if (validateVer(elem)) {
    $(elem).data('last-valid-version', $(elem).val());
  } else {
    var lastValidVersion = $(elem).data('last-valid-version');
    if (lastValidVersion != null) {
      $(elem).val(lastValidVersion);
    } else {
      $(elem).val('1.0');
    }
  }
}

And change your text field to call changeIfValid for the onChange event:

text_field_tag('version', 
               version, 
               :cols => 20, 
               :onchange => "changeIfValid(this);")

EDIT: In order to initialize data-last-valid-version or set any of the other attributes for the text_field_tag , you can just pass it as a hash value to the text_field_tag method:

text_field_tag('version', 
               version, 
               :cols => 20, 
               "data-last-valid-version" => "A_DEFAULT_VAL",
               :onchange => "changeIfValid(this);")

By the way, data-* attributes are a feature of HTML 5 not Rails. Even if you are using HTML 4 or XHTML, jQuery can still handle them for you.