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

/*!
{
  "name": "Form Validation",
  "property": "formvalidation",
  "tags": ["forms", "validation", "attribute"],
  "builderAliases": ["forms_validation"]
}
!*/
/* DOC
This implementation only tests support for interactive form validation.
To check validation for a specific type or a specific other constraint,
the test can be combined:

- `Modernizr.inputtypes.number && Modernizr.formvalidation` (browser supports rangeOverflow, typeMismatch etc. for type=number)
- `Modernizr.input.required && Modernizr.formvalidation` (browser supports valueMissing)
*/
define(['Modernizr', 'createElement', 'docElement', 'testStyles'], function(Modernizr, createElement, docElement, testStyles) {
  Modernizr.addTest('formvalidation', function() {
    var form = createElement('form');
    if (!('checkValidity' in form) || !('addEventListener' in form)) {
      return false;
    }
    if ('reportValidity' in form) {
      return true;
    }
    var invalidFired = false;
    var input;

    Modernizr.formvalidationapi = true;

    // Prevent form from being submitted
    form.addEventListener('submit', function(e) {
      // Old Presto based Opera does not validate form, if submit is prevented
      // although Opera Mini servers use newer Presto.
      if (!window.opera || window.operamini) {
        e.preventDefault();
      }
      e.stopPropagation();
    }, false);

    // Calling form.submit() doesn't trigger interactive validation,
    // use a submit button instead
    //older opera browsers need a name attribute
    form.innerHTML = '<input name="modTest" required="required" /><button></button>';

    testStyles('#modernizr form{position:absolute;top:-99999em}', function(node) {
      node.appendChild(form);

      input = form.getElementsByTagName('input')[0];

      // Record whether "invalid" event is fired
      input.addEventListener('invalid', function(e) {
        invalidFired = true;
        e.preventDefault();
        e.stopPropagation();
      }, false);

      //Opera does not fully support the validationMessage property
      Modernizr.formvalidationmessage = !!input.validationMessage;

      // Submit form by clicking submit button
      form.getElementsByTagName('button')[0].click();
    });

    return invalidFired;
  });
});