az-func-middleware

Simple middleware for Azure Functions

Installation

npm install az-func-middleware

Usage

Let's say you have the following HTTP Trigger:

const httpTrigger: AzureFunction = async function (context: Context): Promise<void> {
  context.res = {
    body: "This HTTP triggered function executed successfully."
  }
}

export default httpTrigger

You can simply wrap it using the withMiddleware function and pass an array of middlewares:

import { withMiddleware, Next } from 'az-func-middleware'

const myMiddleware = async (context: Context, next: Next) => {
  // run your logic
  // ...

  // call next() whenever you want to invoke the next middleware in the chain
  await next(context)
}

export default withMiddleware(httpTrigger, [myMiddleware])

Use cases

Mutating the context in your middleware

import { withMiddleware, Next } from 'az-func-middleware'

const myMiddleware = async (context: Context, next: Next) => {
  context.res = {
    status: 401,
    body: { message: 'You do not have access' }
  }

  // call next depending on your use-case
  await next(context)
}

export default withMiddleware(httpTrigger, [myMiddleware])

Make sure your function does not execute when the response is already set.

const httpTrigger: AzureFunction = async function (context: Context): Promise<void> {
  if(context.res) return
}

export default withMiddleware(httpTrigger, [myMiddleware])