Building smart functions

Smart functions are written and run in ordinary TypeScript, but you must still build them with the Jstz dependencies before deploying them.

For examples of smart function projects, see the examples folder: https://github.com/jstz-dev/jstz/tree/main/examples.

Follow these steps to create and build a TypeScript project for your smart function:

1. Create a package.json file appropriate for a TypeScript project. You can use the npm init command, the yarn init command, or create a package.json file manually to describe the project.

2. Add the @jstz-dev/jstz dependency and esbuild build dependencies.

3. Add a build script that looks like this, with the name of your smart function source file in place of the variable <SOURCE_FILE>:

   esbuild <SOURCE_FILE> --bundle --format=esm --target=esnext --minify --outfile=dist/index.js

   Here is an example of a package.json file for a smart function project:

   {
     "name": "my-smart-function",
     "authors": "",
     "version": "0.0.0",
     "main": "index.ts",
     "dependencies": {
       "@jstz-dev/jstz": "^0.0.0"
     },
     "devDependencies": {
       "esbuild": "^0.20.2"
     },
     "scripts": {
       "build": "esbuild index.ts --bundle --format=esm --target=esnext --minify --outfile=dist/index.js"
     }
   }

4. Add a tsconfig.json file to specify how TypeScript builds the file, including accessing types for Jstz code, as in this example:

   {
     "compilerOptions": {
       "lib": ["esnext"],
       "module": "esnext",
       "target": "esnext",
       "strict": true,
       "moduleResolution": "node",
       "types": ["@jstz-dev/types"]
     },
     "exclude": ["node_modules"]
   }

5. Install the dependencies by running npm install or yarn install.

6. Add the code of your smart function to a TypeScript file in the project and make sure that the build script builds it. For example, you can use the example smart function in Smart functions or any of the smart functions in the examples folder.

7. Build the smart function with the build script, either by running npm run build or yarn build. Jstz builds the smart function with the necessary dependencies and writes the output to dist/index.ts.

Now you can deploy the smart function to the local sandbox. See Deploying.

tip

You can verify the size of the built smart function with the du command, as in du -bh dist/index.ts. Smart functions must be less than 10MB to be deployed.