AutoAPI-JS

Build TypeScript and JavaScript functions automatically into a REST API

Note: it is HIGHLY recommended that you use TypeScript. The typing system using in TypeScript will let you produce a much more reliable and better documented API

Installing

This package can be added to an existing Node project via the command npm install @automatique/autoapi-js

Usage

AutoAPI-JS currently exports one function, buildExpress. The purpose of this package is to automatically build REST APIs from simple JavaScript/TypeScript functions. The functions that are turned into APIs are those that are in the default export(typescript or javascript) or module.exports =(javascript) of the main file specified to buildExpress

Hello Automatique: TypeScript

index.ts:

function hello(): string {
  return "Hello world";
}

export default {
  hello: hello,
};

Running the below buildTSExpress function with the above snippet in index.ts will generate an API, with a single path, /hello which executes and returns the result of the function hello()

// Build an API
buildExpress(
  // Project root
  "/some/path/to/a/typescript/project",
  // Main file
  "index.ts",
  // Options
  { newSource: "app.ts", language: "TypeScript", port: 5000 }
);

The above returns an object with three attributes, "index", the text of an index.ts script, "packageJSON", a JSON object representing a package.json file, and "tsConfig", a valid typescript config JSON object. Additionally, it returns "routeData", which provides a summary of the generated API

Hello Automatique: JavaScript

index.js

function hello() {
  return "Hello world";
}
module.exports = {
  hello,
};

// Build an API
buildExpress(
  // Project root
  "/some/path/to/a/typescript/project",
  // Main file
  "index.js",
  // Options
  { language: "JavaScript" }
);

A More Complex Example

APIs can also be built with nested exports, creating more structured endpoints. For example, consider a Math API. We can build hierarchical exports, to export both functions and constants

function calculateArea(length: number, height: number) {
  return length * height;
}

/**
 * @param {number} n the number to generate a factorial for
 * @return {number} the calculated factorial
 */

function factorial(n: number) {
  if (n === 1) return 1;
  return n * factorial(n - 1);
}
export default {
  geometry: {
    area: calculateArea,
    volume: (x: number, y: number, z: number) => x * y * z,
  },
  factorial,
  constants: {
    pi: () => 3.14159,
    e: () => 2.71828,
  },
};

As in the above, we can fluidly mix externally declared functions, shorthand object notation and arrow functions. The above example will generate an API with paths

/geometry/area
/geometry/volume
/factorial
/constants/pi
/constants/e

Additionally, any JSDoc will be preserved in the generated API, such as the one for the function factorial above.

Optional Arguments

Normally, the generated API will perform a check for the existance of any declared parameters for a function. The exception to this is if an initializer is provided or (typescript) the parameter is marked nullable. For example:

function hello(name: string) {
  return `hello ${name}`;
}
function goodbye(name?: string) {
  if (name) return `Goodbye ${name}`;
  else return "Goodbye stranger";
}
export default {
  hello,
  goodbye,
};

In the generated API, calling /hello will result in a 400 response code, returning {error: "missing parameter name"}. However, calling /goodbye?name=foobar and /goodbye will both return a 200 response code

Notes

There are some changes in the source file that must be made to correctly work

1. URL Paths are case-insensitive, unlike JavaScript/TypeScript identifiers. If you attempt to export 2 functions with the same name, differing by casing (eg foo() and FOO()), undefined behaviour will occur

2. Because of the need to interface with other languages, and work across the network, there are some restrictions on parameter and return types for functions. Return types may not include unions, unless the union can be coerced to a base type. For example, returning type "foo" | "bar" is permitted (and will be coerced to type string), but returning type string | 5 is not permitted. Additionally, promises cannot be parameters, and any return may only have a promise at the top level. For example, a function may return Promise<string> but cannot return {foo: string, prom: Promise<string>}

Contributing

autoapi-js is an open-source project by Automatique. If you encounter bugs, find problems or just want to contribute features, feel free to either open an issue or fork and make a pull request