Question

I am using Ruby on Rails v3.0.9 and jQuery v1.6.1. I would like to handle (by using jQuery) a JSON response data when the AJAX HTTP request returns an error (see the code below for more information) in order to display @user.errors messages. That is, …

… in the controller I have:

render :json   => @user.errors,
       :status => 400

… in the view file I have:

$jQ.ajax({
  type:     '...',
  url:      '...',
  dataType: 'json',
  data:     '...',
  error:    function(jqXHR, textStatus, errorThrown) {

    // Here is where I would like to handle the above mentioned `@user.errors` 
    // array (that is related to the "Ruby on Rails Way" of handling errors).
    //
    // I tried to use 'alert(jqXHR.base);' but the `@user.errors` array is always
    // returned as a string.
    alert(...)

  },
  success:  function(data, textStatus, jqXHR) {
    ...
  }
});

There is a way to change the above code so to use something like the following in order to display errors?

# Supposing that'@user.errors' is '{"base":["already exist"]}'
alert(jqXHR.base);

Note: In few words, I would like to handle data as made when I get a success AJAX HTTP request data (function(data, textStatus, jqXHR)‘s permits me to use the JSON parsed data like so: alert(jqXHR.base);).

Answer 1

This is pretty simple. You just need to json-decode the answer returned by the server. Simply use http://api.jquery.com/jQuery.parseJSON/ to do that.