babel-plugin-transform-custom-element-classes
Compile Custom Element classes that extend HTMLElement
for ES5 environments.
Problem
Custom Elements were designed for native ES6 classes that can extend host objects in ways prototypical inheritance can not. Using the Babel transform-es2015-classes
transform will not work as is. You'll likely see a runtime error like "Uncaught TypeError: Failed to construct 'HTMLElement': Please use the 'new' operator, this DOM object constructor cannot be called as a function."
when attempting to extend HTMLElement
in a Babel transpiled class.
Solution
A workaround is to use Reflect.construct
to build a new HTMLElement
instance expected by the constructor. This transform wraps any ES6 classes extending HTMLElement
with an intermediary class that shims this behavior.
Compatibility
- Chrome Works as is
- Safari 10.1 Technology Preview Works as is
- Safari 10 Stable Requires Custom Elements V1 polyfill
- Firefox Requires Custom Elements V1 polyfill
- Edge Requires Custom Elements V1 polyfill
- IE11 Requires Custom Elements V1 polyfill and
Reflect.construct
polyfill
Installation
$ npm install babel-plugin-transform-custom-element-classes
Usage
.babelrc
Via .babelrc
// include before transform-es2015-classes "plugins": "transform-custom-element-classes" "transform-es2015-classes"