welsonjs/node_modules/modernizr/feature-detects/forms/formattribute.js

/*!
{
  "name": "input[form] Attribute",
  "property": "formattribute",
  "tags": ["attribute", "forms", "input"],
  "builderAliases": ["forms_formattribute"]
}
!*/
/* DOC
Detects whether input form="form_id" is available on the platform
E.g. IE 10 (and below), don't support this
*/
define(['Modernizr', 'createElement', 'docElement'], function(Modernizr, createElement, docElement) {

  Modernizr.addTest('formattribute', function() {
    var form = createElement('form');
    var input = createElement('input');
    var div = createElement('div');
    var id = 'formtest' + (new Date()).getTime();
    var attr;
    var bool = false;

    form.id = id;

    //IE6/7 confuses the form idl attribute and the form content attribute, so we use document.createAttribute
    try {
      input.setAttribute('form', id);
    }
    catch (e) {
      if (document.createAttribute) {
        attr = document.createAttribute('form');
        attr.nodeValue = id;
        input.setAttributeNode(attr);
      }
    }

    div.appendChild(form);
    div.appendChild(input);

    docElement.appendChild(div);

    bool = form.elements && form.elements.length === 1 && input.form === form;

    div.parentNode.removeChild(div);
    return bool;
  });
});