# XSLT Polyfill
This is a polyfill for the [XSLT W3C 1.0](https://www.w3.org/TR/xslt-10/)
standard, roughly as shipped in the Chrome browser. It is intended as a
replacement for using the XSLT processing machinery built into browsers. It
does still rely on the XML parsing machinery (e.g. `parseFromString(xmlText,
"application/xml")`) for some things.
Note that the XSLT 1.0 standard is *very* old, and XSLT has evolved well
beyond the version shipped in web browsers. There are also more up-to-date
JS-based implementations of XSLT that support the most current standards.
One such example is [SaxonJS](https://www.saxonica.com/saxonjs/index.xml).
You should check that out if you're looking for "real" XSLT support; this
polyfill is intended merely as a stopgap that can be used to maintain
functionality.
## Usage
If you have an XML document that contains an XSL processing instruction, like
this:
```xml
Hello World.
```
You can convert it to use this polyfill by simply adding the polyfill directly
to the XML, like this (note the new `
Hello World.
```
This will automatically load the XML and XSLT, process it with this
XSLT polyfill, and replace the page with the result of the transformation.
The example above is available in the `test/` folder of this repo:
[`demo.xml`](https://github.com/mfreed7/xslt_polyfill/blob/main/test/demo.xml).
The polyfill also provides a full implementation of the `XSLTProcessor` class,
so that code like this will also work:
```html
```
The example above is available in the `test/` folder of this repo:
[`XSLTProcessor_example.html`](https://github.com/mfreed7/xslt_polyfill/blob/main/test/XSLTProcessor_example.html).
## Loading Spinner
When the polyfill is used to automatically transform a page (e.g. via an
injected `
```
You can also dynamically set or clear the spinner at runtime by modifying the
property:
```javascript
// Show the spinner with new text
window.xsltPolyfillSpinner = 'Updating content...';
// Hide the spinner and show the document body
window.xsltPolyfillSpinner = null;
```
## Implementation
The polyfill is powered by a WebAssembly port of the
[libxslt](https://gitlab.gnome.org/GNOME/libxslt) and
[libxml2](https://gitlab.gnome.org/GNOME/libxml2) C libraries, providing a
standards-compliant XSLT 1.0 engine.
- **XSLTProcessor Polyfill**: Implements the full `XSLTProcessor` API, including
`importStylesheet`, `transformToDocument`, `transformToFragment`, and
parameter management.
- **Automatic Transformation**: When included via a `