Manipulation: Avoid concatenating strings in buildFragment

Concatenating HTML strings in buildFragment is a possible security risk as it
creates an opportunity of escaping the concatenated wrapper. It also makes it
impossible to support secure HTML wrappers like
[trusted types](https://web.dev/trusted-types/). It's safer to create wrapper
elements using `document.createElement` & `appendChild`.

The previous way was needed in jQuery <4 because IE <10 doesn't accept table
parts set via `innerHTML`, even if the element which contents are set is
a proper table element, e.g.:
```js
tr.innerHTML = "<td></td>";
```
The whole structure needs to be passed in one HTML string. jQuery 4 drops
support for IE <11 so this is no longer an issue; in older version we'd have
to duplicate the code paths.

IE <10 needed to have `<option>` elements wrapped in
`<select multiple="multiple">` but we no longer need that on master which
makes the `document.createElement` way shorter as we don't have to call
`setAttribute`.

All these improvements, apart from making logic more secure, decrease the
gzipped size by 58 bytes.

Closes gh-4724
Ref gh-4409
Ref angular/angular.js#17028

Co-authored-by: Richard Gibson <richard.gibson@gmail.com>

0 files changed, 0 insertions, 0 deletions