Fast TypeScript runner and register hook with eager compilation.

Similar to ts-node, except it uses esbuild – an extremely fast TypeScript transpiler – to eagerly compile all included files from your tsconfig.json on startup. This makes a noticeable difference for tasks where you're likely to load a good portion of your TS files, eg running tests.

It falls back to lazy compilation if a file is require'd that's not in tsconfig.json, and will also fallback to ts-node (if it's installed) for any type-specific compilation that esbuild doesn't support (such as emitDecoratorMetadata). It will also optionally require tsconfig-paths for paths support if your tsconfig needs it.

npm install -D ts-eager

# Optional, but recommended: for determining files from tsconfig.json
npm install -D typescript

# Optional, if you need emitDecoratorMetadata support
npm install -D ts-node

# Optional, if you need paths support
npm install -D tsconfig-paths

ts-eager myfile.ts

Or as a require hook:

node -r ts-eager/register myfile.ts

ts-eager doesn't have any specific command-line options – it invokes node and passes all command-line arguments through.

It supports these environment variables:

• TS_EAGER_LOGLEVEL: 'error' (default), 'warning', 'info', 'silent'
• TS_NODE_PROJECT: tsconfig file (default tsconfig.json)
• TS_NODE_IGNORE: comma separated regexes to skip compilation completely

If you want to customize which files ts-eager compiles up-front, you can specify a different tsconfig.json using TS_NODE_PROJECT, and then use the standard TypeScript include/exclude options in your config.

For example, if this was in tsconfig.test.json:

{
  "extends": "./tsconfig.json",
  "include": ["test"],
  "exclude": ["**/*.template.ts"]
}

Then you could run mocha like this:

TS_NODE_PROJECT=tsconfig.test.json mocha -r ts-eager/register

And it would only eagerly compile files in test, and exclude any matching *.template.ts.

mocha also supports adding require hooks in .mocharc.json:

{
  "recursive": true,
  "require": ["ts-eager/register"],
  "timeout": 5000
}