system.js

/**
 * Internal function to check using Ajax if clean URLs can be enabled on the
 * settings page.
 *
 * This function is not used to verify whether or not clean URLs
 * are currently enabled.
 */
Drupal.behaviors.cleanURLsSettingsCheck = function(context) {
  // This behavior attaches by ID, so is only valid once on a page.
  // Also skip if we are on an install page, as Drupal.cleanURLsInstallCheck will handle
  // the processing.
  if ($("#clean-url.clean-url-processed, #clean-url.install").size()) {
    return;
  }
  var url = Drupal.settings.basePath +"admin/settings/clean-urls/check";
  $("#clean-url .description span").html('<div id="testing">'+ Drupal.t('Testing clean URLs...') +"</div>");
  $("#clean-url p").hide();
  $.ajax({
    url: location.protocol +"//"+ location.host + url,
    dataType: 'json',
    success: function () {
      // Check was successful.
      $("#clean-url input.form-radio").attr("disabled", false);
      $("#clean-url .description span").append('<div class="ok">'+ Drupal.t('Your server has been successfully tested to support this feature.') +"</div>");
      $("#testing").hide();
    },
    error: function() {
      // Check failed.
      $("#clean-url .description span").append('<div class="warning">'+ Drupal.t('Your system configuration does not currently support this feature. The <a href="http://drupal.org/node/15365">handbook page on Clean URLs</a> has additional troubleshooting information.') +"</div>");
      $("#testing").hide();
    }
  });
  $("#clean-url").addClass('clean-url-processed');
};

/**
 * Internal function to check using Ajax if clean URLs can be enabled on the
 * install page.
 *
 * This function is not used to verify whether or not clean URLs
 * are currently enabled.
 */
Drupal.cleanURLsInstallCheck = function() {
  var url = location.protocol +"//"+ location.host + Drupal.settings.basePath +"admin/settings/clean-urls/check";
  $("#clean-url .description").append('<span><div id="testing">'+ Drupal.settings.cleanURL.testing +"</div></span>");
  $("#clean-url.install").css("display", "block");
  $.ajax({
    url: url,
    dataType: 'json',
    success: function () {
      // Check was successful.
      $("#clean-url input.form-radio").attr("disabled", false);
      $("#clean-url input.form-radio").attr("checked", 1);
      $("#clean-url .description span").append('<div class="ok">'+ Drupal.settings.cleanURL.success +"</div>");
      $("#testing").hide();
    },
    error: function() {
      // Check failed.
      $("#clean-url .description span").append('<div class="warning">'+ Drupal.settings.cleanURL.failure +"</div>");
      $("#testing").hide();
    }
  });
  $("#clean-url").addClass('clean-url-processed');
};

/**
 * When a field is filled out, apply its value to other fields that will likely
 * use the same value. In the installer this is used to populate the
 * administrator e-mail address with the same value as the site e-mail address.
 */
Drupal.behaviors.copyFieldValue = function (context) {
  for (var sourceId in Drupal.settings.copyFieldValue) {
    // Get the list of target fields.
    targetIds = Drupal.settings.copyFieldValue[sourceId];
    if (!$('#'+ sourceId + '.copy-field-values-processed').size(), context) {
      // Add the behavior to update target fields on blur of the primary field.
      sourceField = $('#' + sourceId);
      sourceField.bind('blur', function() {
        for (var delta in targetIds) {
          var targetField = $('#'+ targetIds[delta]);
          if (targetField.val() == '') {
            targetField.val(this.value);
          }
        }
      });
      sourceField.addClass('copy-field-values-processed');
    }
  }
};

/**
 * Show/hide custom format sections on the date-time settings page.
 */
Drupal.behaviors.dateTime = function(context) {
  // Show/hide custom format depending on the select's value.
  $('select.date-format:not(.date-time-processed)', context).change(function() {
    $(this).addClass('date-time-processed').parents("div.date-container").children("div.custom-container")[$(this).val() == "custom" ? "show" : "hide"]();
  });

  // Attach keyup handler to custom format inputs.
  $('input.custom-format:not(.date-time-processed)', context).addClass('date-time-processed').keyup(function() {
    var input = $(this);
    var url = Drupal.settings.dateTime.lookup +(Drupal.settings.dateTime.lookup.match(/\?q=/) ? "&format=" : "?format=") + encodeURIComponent(input.val());
    $.getJSON(url, function(data) {
      $("div.description span", input.parent()).html(data);
    });
  });

  // Trigger the event handler to show the form input if necessary.
  $('select.date-format', context).trigger('change');
};