Build API clients for TypeScript
In this tutorial, you build a sample app in TypeScript that calls a REST API that doesn't require authentication.
Required tools
Create a project
Run the following commands in the directory where you want to create a new project.
npm init
npm install -D typescript @types/node
npx tsc --init
Project configuration
In case you're adding a Kiota client to an existing project, the following configuration is required:
- tsconfig > compilerOptions > esModuleInterop set to "true".
- tsconfig > compilerOptions > forceConsistentCasingInFileNames set to "true".
- tsconfig > compilerOptions > lib with an entry of "es2015".
- tsconfig > compilerOptions > module set to "NodeNext".
- tsconfig > compilerOptions > moduleResolution set to "NodeNext".
- tsconfig > compilerOptions > target set to "es2020" or later.
- package.json > type set to "module".
Add dependencies
Before you can compile and run the generated API client, you need to make sure the generated source files are part of a project with the required dependencies. Your project must have a reference to the bundle package. For more information about Kiota dependencies, see the dependencies documentation.
Run the following commands to get the required dependencies.
npm install @microsoft/kiota-bundle
Generate the API client
Kiota generates API clients from OpenAPI documents. Create a file named posts-api.yml and add the following.
openapi: '3.0.2'
info:
title: JSONPlaceholder
version: '1.0'
servers:
- url: https://jsonplaceholder.typicode.com/
components:
schemas:
post:
type: object
properties:
userId:
type: integer
id:
type: integer
title:
type: string
body:
type: string
parameters:
post-id:
name: post-id
in: path
description: 'key: id of post'
required: true
style: simple
schema:
type: integer
paths:
/posts:
get:
description: Get posts
parameters:
- name: userId
in: query
description: Filter results by user ID
required: false
style: form
schema:
type: integer
maxItems: 1
- name: title
in: query
description: Filter results by title
required: false
style: form
schema:
type: string
maxItems: 1
responses:
'200':
description: OK
content:
application/json:
schema:
type: array
items:
$ref: '#/components/schemas/post'
post:
description: 'Create post'
requestBody:
required: true
content:
application/json:
schema:
$ref: '#/components/schemas/post'
responses:
'201':
description: Created
content:
application/json:
schema:
$ref: '#/components/schemas/post'
/posts/{post-id}:
get:
description: 'Get post by ID'
parameters:
- $ref: '#/components/parameters/post-id'
responses:
'200':
description: OK
content:
application/json:
schema:
$ref: '#/components/schemas/post'
patch:
description: 'Update post'
requestBody:
required: true
content:
application/json:
schema:
$ref: '#/components/schemas/post'
parameters:
- $ref: '#/components/parameters/post-id'
responses:
'200':
description: OK
content:
application/json:
schema:
$ref: '#/components/schemas/post'
delete:
description: 'Delete post'
parameters:
- $ref: '#/components/parameters/post-id'
responses:
'200':
description: OK
This file is a minimal OpenAPI description that describes how to call the /posts
endpoint in the JSONPlaceholder REST API.
You can then use the Kiota command line tool to generate the API client classes.
kiota generate -l typescript -d posts-api.yml -c PostsClient -o ./client
Tip
Add --exclude-backward-compatible
if you want to reduce the size of the generated client and are not concerned about
potentially source breaking changes with future versions of Kiota when updating the client.
Create the client application
Create a file in the root of the project named index.ts and add the following code.
import { AnonymousAuthenticationProvider } from "@microsoft/kiota-abstractions";
import { FetchRequestAdapter } from "@microsoft/kiota-http-fetchlibrary";
import { createPostsClient } from "./client/postsClient.js";
import { Post } from "./client/models/index.js";
// API requires no authentication, so use the anonymous
// authentication provider
const authProvider = new AnonymousAuthenticationProvider();
// Create request adapter using the fetch-based implementation
const adapter = new FetchRequestAdapter(authProvider);
// Create the API client
const client = createPostsClient(adapter);
async function main(): Promise<void> {
try {
// GET /posts
const allPosts = await client.posts.get();
console.log(`Retrieved ${allPosts?.length} posts.`);
// GET /posts/{id}
const specificPostId = 5;
const specificPost = await client.posts.byPostId(specificPostId).get();
console.log(
`Retrieved post - ID: ${specificPost?.id}, Title: ${specificPost?.title}, Body: ${specificPost?.body}`
);
// POST /posts
const newPost: Post = {
userId: 42,
title: "Testing Kiota-generated API client",
body: "Hello world!",
};
const createdPost = await client.posts.post(newPost);
console.log(`Created new post with ID: ${createdPost?.id}`);
// PATCH /posts/{id}
const update: Post = {
// Only update title
title: "Updated title",
};
const updatedPost = await client.posts
.byPostId(specificPostId)
.patch(update);
console.log(
`Updated post - ID: ${updatedPost?.id}, Title: ${updatedPost?.title}, Body: ${updatedPost?.body}`
);
// DELETE /posts/{id}
await client.posts.byPostId(specificPostId).delete();
} catch (err) {
console.log(err);
}
}
main();
Note
The JSONPlaceholder REST API doesn't require any authentication, so this sample uses the AnonymousAuthenticationProvider. For APIs that require authentication, use an applicable authentication provider.
Run the application
To start the application, run the following command in your project directory.
tsc && node out/index.js
See also
- kiota-samples repository contains the code from this guide.
- Microsoft Graph sample using Microsoft identity platform authentication
- ToDoItem Sample API implements a sample OpenAPI in ASP.NET Core and sample clients in multiple languages.