Using TypeScript
While CAP itself is written in JavaScript, it's possible to use TypeScript within your project as outlined here.
Enable TypeScript Support
Follow these steps to add TypeScript support:
Install typescript packages globally:
shnpm i -g typescript ts-node
npm i -g typescript ts-node
Add a tsconfig.json file to your project.
You need to provide a tsconfig.json file in which you configure how you want to use TypeScript. See the official TypeScript documentation for more details.
Developing with cds-ts
Use the cds-ts
CLI command instead of cds
to avoid having to precompile TypeScript files to JavaScript each time and speed up development:
cds-ts serve world.cds
cds-ts serve world.cds
cds-ts watch
cds-ts watch
When using the binary cds-ts
, the ts-node engine is used to start the project instead of the default node engine.
WARNING
Note that this binary should be used for development only. For productive usage always precompile TypeScript code to JavaScript due to performance reasons and use the cds
binary.
Writing TypeScript Files
Once you've setup everything correctly, you can start writing TypeScript files instead of JavaScript files. This applies for service handlers, as well as a custom server.ts file or database init.ts seeding files.
Samples
You can also download the Hello World! TypeScript sample or try out the Full Stack TypeScript App.
Testing with ts-jest
Run your Jest tests with preset ts-jest
without precompiling TypeScript files.
Install
ts-jest
locally:shnpm add ts-jest
npm add ts-jest
Tell Jest to use the preset
ts-jest
, e.g. in your jest.config.js:jsmodule.exports = { preset: "ts-jest", globalSetup: "./test/setup.ts" };
module.exports = { preset: "ts-jest", globalSetup: "./test/setup.ts" };
Set
CDS_TYPESCRIPT
environment variable:This is necessary, because it isn't possible to programmatically detect that the preset
ts-jest
is used and we've to know whether we need to look for .ts or .js files.File ./test/setup.ts, content:
jsmodule.exports = async () => { p
rocess.env. CDS_TYPESCRIPT = "true"; };module.exports = async () => { p
rocess.env. CDS_TYPESCRIPT = "true"; };Run your tests as usual:
shjest
jest
TypeScript APIs in @sap/cds
The package @sap/cds
is shipped with TypeScript declarations. These declarations are used automatically when you write TypeScript files, but also enable IntelliSense and type checking for standard JavaScript development in Visual Studio Code.
WARNING
As @sap/cds
is a JavaScript library, typings aren't always up to date. You should expect a delay for typings related to the latest release, even gaps, and errors.
TIP
We invite you to contribute and help us complete the typings as appropriate. Sounds interesting? Reach out to us.
Enhanced TypeScript Support
CAP envisions to enhance the TypeScript support and, for example, generate TypeScript interfaces for definitions in CDS models. But it's important to know, that this isn't planned in our roadmap (yet).
There are already community contributions that fill in this gap.
See the blog post by Simon Gaudeck for more details.