Vanilla JS や TypeScript で Custom Elements を書く際の注意点 ref: https://qiita.com/jimbo/items/d17a121f815236c2f55b

file0.txt

Failed to construct 'HTMLElement': Please use the 'new' operator, this DOM object constructor cannot be called as a function.

file2.txt

{
  "presets": ["env"],
  "plugins": ["transform-custom-element-classes"]
}

tsconfig.json

{
  "compilerOptions": {
    "target": "ES6"
  },
  "include": ["src/**/*"],
  "exclude": ["node_modules"]
}