createFragment method Null safety

DocumentFragment createFragment (
  1. String? svg,
  2. {NodeValidator? validator,
  3. NodeTreeSanitizer? treeSanitizer}

Create a DocumentFragment from the HTML fragment and ensure that it follows the sanitization rules specified by the validator or treeSanitizer.

If the default validation behavior is too restrictive then a new NodeValidator should be created, either extending or wrapping a default validator and overriding the validation APIs.

The treeSanitizer is used to walk the generated node tree and sanitize it. A custom treeSanitizer can also be provided to perform special validation rules but since the API is more complex to implement this is discouraged.

The returned tree is guaranteed to only contain nodes and attributes which are allowed by the provided validator.

See also:


DocumentFragment createFragment(String? svg,
    {NodeValidator? validator, NodeTreeSanitizer? treeSanitizer}) {
  if (treeSanitizer == null) {
    if (validator == null) {
      validator = new NodeValidatorBuilder.common()..allowSvg();
    treeSanitizer = new NodeTreeSanitizer(validator);

  // We create a fragment which will parse in the HTML parser
  var html = '<svg version="1.1">$svg</svg>';
  var fragment =
      document.body!.createFragment(html, treeSanitizer: treeSanitizer);

  var svgFragment = new DocumentFragment();
  // The root is the <svg/> element, need to pull out the contents.
  var root = fragment.nodes.single;
  while (root.firstChild != null) {
  return svgFragment;