Remove all attributes

A simple method that doesn't require JQuery:

while(elem.attributes.length > 0)
    elem.removeAttribute(elem.attributes[0].name);

Update: the previous method works in IE8 but not in IE8 compatibility mode and previous versions of IE. So here is a version that does and uses jQuery to remove the attributes as it does a better job of it:

$("img").each(function() {
  // first copy the attributes to remove
  // if we don't do this it causes problems
  // iterating over the array we're removing
  // elements from
  var attributes = $.map(this.attributes, function(item) {
    return item.name;
  });

  // now use jQuery to remove the attributes
  var img = $(this);
  $.each(attributes, function(i, item) {
    img.removeAttr(item);
  });
});

Of course you could make a plug-in out of it:

jQuery.fn.removeAttributes = function() {
  return this.each(function() {
    var attributes = $.map(this.attributes, function(item) {
      return item.name;
    });
    var img = $(this);
    $.each(attributes, function(i, item) {
    img.removeAttr(item);
    });
  });
}

and then do:

$("img").removeAttributes();

One-liner, no jQuery needed:

[...elem.attributes].forEach(attr => elem.removeAttribute(attr.name));