# LitElement TypeScript starter 

This project includes a sample component using LitElement with TypeScript.

## Setup

Install dependencies:

```bash
npm i
```

## Build

This sample uses the TypeScript compiler to produce JavaScript that runs in modern browsers.

To build the JavaScript version of your component:

```bash
npm run build
```

To watch files and rebuild when the files are modified, run the following command in a separate shell:

```bash
npm run build:watch
```

Both the TypeScript compiler and lit-analyzer are configured to be very strict. You may want to change `tsconfig.json` to make them less strict.

## Testing

This sample uses Karma, Chai, Mocha, and the open-wc test helpers for testing. See the [open-wc testing documentation](https://open-wc.org/testing/testing.html) for more information.

Tests can be run with the `test` script:

```bash
npm test
```

## Dev Server

This sample uses open-wc's [es-dev-server](https://github.com/open-wc/open-wc/tree/master/packages/es-dev-server) for previewing the project without additional build steps. ES dev server handles resolving Node-style "bare" import specifiers, which aren't supported in browsers. It also automatically transpiles JavaScript and adds polyfills to support older browsers.

To run the dev server and open the project in a new browser tab:

```bash
npm run serve
```
## Editing

If you use VS Code, we highly reccomend the [lit-plugin extension](https://marketplace.visualstudio.com/items?itemName=runem.lit-plugin), which enables some extremely useful features for lit-html templates:
  - Syntax highlighting
  - Type-checking
  - Code completion
  - Hover-over docs
  - Jump to definition
  - Linting
  - Quick Fixes
  
  The project is setup to reccomend lit-plugin to VS Code users if they don't already have it installed.

## Linting

Linting of TypeScript files is provided by [ESLint](eslint.org) and [TypeScript ESLint](https://github.com/typescript-eslint/typescript-eslint). In addition, [lit-analyzer](https://www.npmjs.com/package/lit-analyzer) is used to type-check and lint lit-html templates with the same engine and rules as lit-plugin.

The rules are mostly the recommended rules from each project, but some have been turned off to make LitElement usage easier. The recommended rules are pretty strict, so you may want to relax them by editing `.eslintrc.json` and `tsconfig.json`.

To lint the project run:

```bash
npm run lint
```

## More information

See [Get started](https://lit-element.polymer-project.org/guide/start) on the LitElement site for more information.