Javascript

Build your Backend with Netlify Functions in 20 Minutes

Published Dec 7, 2020

Updated Feb 14, 2023

9 min read

This article was written over 18 months ago and may contain information that is out of date. Some content may be relevant but please refer to the relevant official documentation or available resources for the latest information.

Build your Backend with Netlify Functions in 20 minutes

Netlify makes deploying your front end quick and easy, and Netlify functions makes running a serverless backend just as easy.

In this guide, we'll get setup on how to use Netlify functions. As an indie developer, you should embrace serverless offerings because of their low barrier to entry and generous free tiers. And as an enterprise shop, you should seriously consider them for an extremely cheap, fast, and scalable way to build out your backend infrastructure.

Use Cases - What can you build?

Modern JavaScript frameworks allow us to build large and complex applications on the client, but they can occasionally run into limitations. For everything else, there's the "backend" which excels at handling some of these use cases:

Protecting Secrets & Credentials
Server Side Rendering
Sending Emails
Handling File IO
Running centralized logic
Executing tasks off the main thread
Bypassing CORS issues for locked down APIs
Providing Progressive Enhancement / NoScript Fallback

Composition of a Function

Netlify Functions provides a wrapper around AWS Lambdas. While the Netlify documentation should be sufficient, it's good to know that there's an escape hatch if you ever want to run on your own AWS subscription. However, Netlify handles some of the deployment magic for you, so let's start there.

Here's the bare bones of a Netlify function in JavaScript:

exports.handler = async function(event, context) {
    return {
        statusCode: 200,
        body: JSON.stringify({message: "Hello World"})
    };
}

If you're familiar with running JavaScript on Node, this should look somewhat familiar. Each function should live in its own file, and will execute whatever is assigned to exports.handler. We have access to event and context. We can run whatever code we need on Node, and return whatever response type we'd like.

To set this up, lets create an empty repository on GitHub. We need to add functions to a folder. While we can use any name, a common pattern is to create a folder name functions. Let's add a file in there called hello.js

//functions/hello.js
exports.handler = async (event, context) => {
  const { name = "Anonymous" } = event.queryStringParameters;
  return {
    statusCode: 200,
    body: `Hello, ${name}`
  };
};

In our function, we can grab information from the query string parameters passed in. We'll destructure those (with a default value) and look for a name param.

To actually wire up our functions folder, we'll need to add a netlify.toml config file at the root of our project.

# netlify.toml
[build]
  functions = "functions/"

Walk Before You Run (Locally)

Our "repo" should look like this at this point:

my-app
├── functions
│   └── hello.js
└── netlify.toml

The best way to run your Netlify site locally, with all the bells and whistles attached, is to use Netlify Dev which you can install via npm:

npm install netlify-cli -g

And then kick off your dev server like this:

netlify dev

Your "site" should now be live at http://localhost:8888. By default, Netlify hosts functions under the subpath /.netlify/functions/<fn-name> so you can invoke your function here:

http://localhost:8888/.netlify/functions/hello?name=Beth

Now, let's make our function's address a little cleaner by also taking advantage of another free Netlify feature using redirects. This allows us to expose the same functions at a terser url by replacing /.netlify/functions with /api.

FROM: <site>/.netlify/functions/hello TO: <site>/api/hello

To do so, append the following info to your netlify.toml config, and restart Netlify dev:

[[redirects]]
  from = '/api/*'
  to = '/.netlify/functions/:splat'
  status = 200

This will route all traffic at /api/* internally to the appropriate functions directory, and the wildcard will capture all additional path info, and move to :splat. By setting the HTTP Status Code = 200, Netlify will preform a "rewrite" (as opposed to a "redirect") which will change the server response without changing the URL in the browser address bar.

So let's try again with our new url:

http://localhost:8888/api/hello?name=Beth

👏 Awesome, you just created a function! (you're following along live, right?)

Getting the CRUD Out & Submitting Data

Now that we can build functions, let's create our own API with some basic CRUD functions (Create, Read, Update, & Delete) for a simple todos app.

One of the central tenants of serverless computing is that it's also stateless. If you need to store any state across function invocations, it should be persisted to another, layer like a database. For this article, let's use the free tier of DynamoDb, but feel free to BYODB (Bring Your Own DB), especially if it has a Node SDK.

In the next steps, we'll:

Setup a table on DynamoDB in AWS
Install npm packages into our project
Setup secret keys in AWS, and add to our environment variables
Initialize the aws-sdk package for NodeJs
And then finally add a Netlify function route to create a record on our database

AWS - Amazon Web Services

This guide will assume some degree of familiarity with AWS & DynamoDB, but if you're new to DynamoDB, you can start with this guide on Getting Started with Node.js and DynamoDB.

On AWS, create a table with the name NetlifyTodos, and string partition key called key.

NPM - Node Package Manager

Now, let's setup npm and install aws-sdk, nanoid, & dotenv.

In a terminal at the root of your project, run the following commands:

npm init -y
npm install aws-sdk nanoid dotenv --save

ENV - Environment Variables

You'll need to provision an access key / secret for an IAM user that we'll use to authenticate our API calls. One of the benefits of running these calls on the server is you're able to protect your application secret through environment variables, instead of having to ship them to the client, which is not recommended.

There are quite a few ways to log into AWS on your local machine, but just to keep everything inside of our project, let's create a .env file at the root of our project, and fill in the following keys with your own values:

# .env
MY_AWS_ACCESS_KEY_ID=***
MY_AWS_SECRET_ACCESS_KEY=***
MY_AWS_REGION=us-east-1

NOTE: One little gotcha here is that the more common AWS_ACCESS_KEY_ID is a reserved environment keyword used by the Netlify process. So if we want to pass around env variables, we'll have to use our own key, in this case prefixed with MY_.

Once they're added to the process, we can destructure them and use in setting up our AWS SDK. We'll need to setup AWS for every CRUD function, so let's assemble all this logic in a separate file called dyno-client.js.

// dyno-client.js
require('dotenv').config()
const { MY_AWS_ACCESS_KEY_ID, MY_AWS_SECRET_ACCESS_KEY, MY_AWS_REGION } = process.env

The following is required.

SDK - Software Developer Kit

Using the aws-sdk makes our life a lot easier for connecting to DynamoDB from our codebase. We can create an instance of the Dynamo client that we'll use for the remaining examples:

// dyno-client.js
const AWS = require("aws-sdk");

AWS.config.update({
    credentials: {
        accessKeyId: MY_AWS_ACCESS_KEY_ID,
        secretAccessKey: MY_AWS_SECRET_ACCESS_KEY
    },
    region: MY_AWS_REGION,
});

const dynamoDb = new AWS.DynamoDB.DocumentClient();

To make this available to all our functions, add the DynamoDB instance to your exports, and we'll grab it when we need it:

module.exports = { dynamoDb, TABLE_NAME }

Create Todo (Due by EOD 😂)

⚡ We're finally ready to create our API function!

In the following example, we'll post back form data containing the text for our todo item. We can parse the form data into JSON, and transform it into an item to insert into our table. If it succeeds, we'll return the result with a status code of 200, and if it fails, we'll return the the error message along with the status code from the error itself.

// functions/create.js
const { nanoid } = require("nanoid");
const { dynamoDb } = require("../dyno-client")

exports.handler = async(event, context) => {
    try {
        // parse form data
        const body = JSON.parse(event.body);

        // create item to insert
        const params = {
            TableName: TABLE_NAME,
            Item: {
                key: nanoid(7),
                text: body.text,
                createDate: new Date().toISOString(),
            },
        };

        let result = await dynamoDb.put(params).promise();

        // return success
        return {
            statusCode: 200,
            body: JSON.stringify({
                success: true,
                data: result,
            }),
        };

    } catch (error) {
        return {
            statusCode: error.statusCode || 500,
            body: JSON.stringify(error),
        };
    }

};

This should give you the gist of how to expose your API routes and logic to perform various operations. I'll hold off on more examples because most of the code here is actually just specific to DynamoDB, and we'll save that for a separate article. But the takeaway is that we're able to return something meaningful with very minimal plumbing. And that's the whole point!

With Functions, you only have to write your own business logic!

Debugging - For Frictionless Feedback Loops

There are two critical debugging tools in Visual Studio Code I like to use when working with node and API routes.

Script Debugger &
Rest Client Plugin

✨ Did you know, instead of configuring a custom launch.json file, you can run and attach debuggers directly onto npm scripts in the package.json file:

And while tools like Postman are a valuable part of comprehensive test suite, you can add the REST Client Extension to invoke API commands directly within VS Code. We can easily use the browser to mock GET endpoints, but this makes it really easy to invoke other HTTP verbs, and post back form data.

Just add a file like test.http to your project. REST Client supports expansion of variable environment, and custom variables. If you stub out multiple calls, you can separate multiple different calls by delimiting with ###.

Add the following to your sample file:

@baseUrl = http://localhost:8888

// create todo item
POST {{baseUrl}}/api/create
content-type: application/json

{
    "text": "Feed the cats",
}

We can now run the above by clicking "Send Request". This should hit our Netlify dev server, and allow us to step through our function logic locally!

Publishing

Publishing to Netlify is easy as well. Make sure your project is committed, and pushed up to a git repository on GitHub, GitLab or BitBucket.

Netlify will prompt for a Build command, and a Publish directory. Believe it or not, we don't actually have either of those things yet, and it's probably a project for another day to set up our front end. Those commands refer to the static site build part of the deployment. Everything we need to build serverless functions is inside our functions directory and our netlify.toml config.

Once we deploy the site, the last thing we'll need to do is add our environment variables to Netlify under Build > Environment

Next Steps - This is only the beginning

Hopefully some ideas are spinning as to how you can use these technologies on your own sites and projects. The focus of this article is on building and debugging Netlify functions, but an important exercise left to the reader is to take advantage of that on your front end.

TIP: If you want to add Create React App to your current directory (without creating a new folder), add a . when scaffolding out a new app like this:

create-react-app .

Try it out - build a front end, and let me know how it goes at KyleMitBTV!

For more context, you can browse the full source code for the article on GitHub at KyleMit/netlify-functions-demo.

For even more practical examples with actual code, checkout the following resources as well!

Good luck, and go build things!

This Dot is a consultancy dedicated to guiding companies through their modernization and digital transformation journeys. Specializing in replatforming, modernizing, and launching new initiatives, we stand out by taking true ownership of your engineering projects.

We love helping teams with projects that have missed their deadlines or helping keep your strategic digital initiatives on course. Check out our case studies and our clients that trust us with their engineering.

About the author(s)

Kyle Mitofsky
Full stack engineer with a love of all things web development. Passionate about inclusion, mentoring, learning, and minimal architectures.
@KyleMitBTV @KyleMit

The HTML Dialog Element: Enhancing Accessibility and Ease of Use

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This is helpful as it reduces the burden on the developer when making their applications accessible by ensuring that user expectations concerning interaction are met, and it can also potentially simplify the implementation of dialogs in general. Basic usage Adding a dialog using the new tag can be achieved with just a few lines of code. ` However, adding the dialog alone won’t do anything to the page. It will show up only once you call the .showModal() method against it. ` Then if you want to close it you can call the .close() method on the dialog, or press the escape key to close it, just like most other modals work. Also, note how a backdrop appears that darkens the rest of the page and prevents you from interacting with it. Neat! Accessibility and focus management Correctly handling focus is important when making your web applications accessible to all users. Typically you have to move the current focus to the active dialog when showing them, but with the dialog element that’s done for you. By default, the focus will be set on the first focusable element in the dialog. You can optionally change which element receives focus first by setting the autofocus attribute on the element you want the focus to start on, as seen in the previous example where that attribute was added to the close element. Using the .showModal() method to open the dialog also implicitly adds the dialog ARIA role to the dialog element. This helps screen readers understand that a modal has appeared and the screen so it can act accordingly. Adding forms to dialogs Forms can also be added to dialogs, and there’s even a special method value for them. If you add a element with the method set to dialog then the form will have some different behaviors that differ from the standard get and post form methods. First off, no external HTTP request will be made with this new method. What will happen instead is that when the form gets submitted, the returnValue property on the form element will be set to the value of the submit button in the form. So given this example form: ` The form element with the example-form id will have its returnValue set to Submit. In addition to that, the dialog will close immediately after the submit event is done being handled, though not before automatic form validation is done. If this fails then the invalid event will be emitted. You may have already noticed one caveat to all of this. You might not want the form to close automatically when the submit handler is done running. If you perform an asynchronous request with an API or server you may want to wait for a response and show any errors that occur before dismissing the dialog. 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Adding React to your ASP.NET MVC web app

Adding React to your ASP.NET MVC web app In this article, we'll take a look how and why you might want to choose React to handle your front end considerations, and let ASP.NET manage the backend Architecture First, let's consider the range of responsibilities that each solution offers: * Templating - scaffolding out HTML markup based on page data * Routing - converting a request into a response * Middleware Pipeline - building assets * Model Binding - building usable model objects from HTML form data * API Services - handling data requests on a server * Client Side Interaction - updating a web page based on user interaction For the most part, both of these frameworks offer ways to handle most of these concerns: | Feature | ASP.NET | React | | ----------------------- |:-------:|:-----:| | Templating | ✔ | ✔ | | Routing | ✔ | ✔ | | Middleware Pipeline | ✔ | | | Model Binding | ✔ | ✔ | | API Services | ✔ | | | Client Side Interaction | | ✔ | Challenges when combining these two technologies include finding which pieces work best together. 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Prerequisites - If you don't have these, you'll need em' * Install dotnet core * Install node & npm * Install vs code Getting Started .NET comes with its own react starter template which is documented here. We'll use it for this example. You can spin up a new project with the dotnet new command like this: ` > Note: If you have Visual Studio, you'll also see the available template starters under the the new project dialog > You should be able to cd into your application directory, open with VS Code, and launch with F5, or by running the following: ` Which will be available at https://localhost:5001/ Net React Starter Let's review what this template adds, and how all the pieces fit together File Structure Here's a very high level view of some of the files involved ` The startup.cs file will wire up the react application as asp.net middleware with the following services / configuration: ` This takes advantage of the Microsoft.AspNetCore.SpaServices.Extensions library on nuget to wire up some of the client side dependencies, and server kick off. 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7 mins

ASP.NETReact

Introduction to Zod for Data Validation

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Unlike TypeScript, Zod schemas aren't removed on compilation to JavaScript—we still have access to them! If our app receives some data, we can verify that it matches the expected shape by passing it to your Zod schema's parse function. You'll either get back your data in exactly the shape you defined in your schema, or Zod will give you an error to tell you what was wrong. Zod schemas aren't a replacement for TypeScript; rather, they are an excellent complement. Once we've defined our Zod schema, it's simple to derive a TypeScript type from it and to use that type as we normally would. But when we really need to be sure our data conforms to the schema, we can always parse the data with our schema for that extra confidence. Defining Data Schemas Zod schemas are the variables that define our expectations for the shape of our data, validate those expectations, and transform the data if necessary to match our desired shape. It's easy to start with simple schemas, and to add complexity as required. Zod provides different functions that represent data structures and related validation options, which can be combined to create larger schemas. In many cases, you'll probably be building a schema for a data object with properties of some primitive type. For example, here's a schema that would validate a JavaScript object representing an order for a pizza: ` Zod provides a number of primitives for defining schemas that line up with JavaScript primitives: string, number, bigint, boolean, date, symbol, undefined, and null. It also includes primitives void, any, unknown, and never for additional typing information. In addition to basic primitives, Zod can define object, array, and other native data structure schemas, as well as schemas for data structures not natively part of JavaScript like tuple and enum. The documentation contains considerable detail on the available data structures and how to use them. Parsing and Validating Data with Schemas With Zod schemas, you're not only telling your program what data should look like; you're also creating the tools to easily verify that the incoming data matches the schema definitions. This is where Zod really shines, as it greatly simplifies the process of validating data like user inputs or third party API responses. Let's say you're writing a website form to register new users. At a minimum, you'll need to make sure the new user's email address is a valid email address. For a password, we'll ask for something at least 8 characters long and including one letter, one number, and one special character. (Yes, this is not really the best way to write strong passwords; but for the sake of showing off how Zod works, we're going with it.) We'll also ask the user to confirm their password by typing it twice. First, let's create a Zod schema to model these inputs: ` So far, this schema is pretty basic. It's only making sure that whatever the user types as an email is an email, and it's checking that the password is at least 8 characters long. But it is *not* checking if password and confirmPassword match, nor checking for the complexity requirements. Let's enhance our schema to fix that! ` By adding refine with a custom validation function, we have been able to verify that the passwords match. If they don't, parsing will give us an error to let us know that the data was invalid. We can also chain refine functions to add checks for our password complexity rules: ` Here we've chained multiple refine functions. You could alternatively use superRefine, which gives you even more fine grained control. Now that we've built out our schema and added refinements for extra validation, we can parse some user inputs. Let's see two test cases: one that's bound to fail, and one that will succeed. ` There are two main ways we can use our schema to validate our data: parse and safeParse. The main difference is that parse will throw an error if validation fails, while safeParse will return an object with a success property of either true or false, and either a data property with your parsed data or an error property with the details of a ZodError explaining why the parsing failed. In the case of our example data, userInput2 will parse just fine and return the data for you to use. But userInput1 will create a ZodError listing all of the ways it has failed validation. ` ` We can use these error messages to communicate to the user how they need to fix their form inputs if validation fails. Each error in the list describes the validation failure and gives us a human readable message to go with it. You'll notice that the validation errors for checking for a valid email and for checking password length have a lot of details, but we've got three items at the end of the error list that don't really tell us anything useful: just a custom error of Invalid input. The first is from our refine checking if the passwords match, and the second two are from our refine functions checking for password complexity (numbers and special characters). Let's modify our refine functions so that these errors are useful! We'll add our own error parameters to customize the message we get back and the path to the data that failed validation. ` Now, our error messages from failures in refine are informative! You can figure out which form fields aren't validating from the path, and then display the messages next to form fields to let the user know how to remedy the error. ` By giving our refine checks a custom path and message, we can make better use of the returned errors. In this case, we can highlight specific problem form fields for the user and give them the message about what is wrong. Integrating with TypeScript Integrating Zod with TypeScript is very easy. Using z.infer<typeof YourSchema> will allow you to avoid writing extra TypeScript types that merely reflect the intent of your Zod schemas. You can create a type from any Zod schema like so: ` Using a TypeScript type derived from a Zod schema does *not* give you any extra level of data validation at the type level beyond what TypeScript is capable of. If you create a type from z.string.min(3).max(20), the TypeScript type will still just be string. And when compiled to JavaScript, even that will be gone! That's why you still need to use parse/safeParse on incoming data to validate it before proceeding as if it really does match your requirements. A common pattern with inferring types from Zod schemas is to use the same name for both. Because the schema is a variable, there's no name conflict if the type uses the same name. However, I find that this can lead to confusing situations when trying to import one or the other—my personal preference is to name the Zod schema with Schema at the end to make it clear which is which. Conclusion Zod is an excellent tool for easily and confidently asserting that the data you're working with is exactly the sort of data you were expecting. It gives us the ability to assert at runtime that we've got what we wanted, and allows us to then craft strategies to handle what happens if that data is wrong. Combined with the ability to infer TypeScript types from Zod schemas, it lets us write and run more reliable code with greater confidence....

Nov 15, 2024

7 mins

JavaScriptZod

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Build your Backend with Netlify Functions in 20 Minutes

Build your Backend with Netlify Functions in 20 minutes

Use Cases - What can you build?

Composition of a Function

Walk Before You Run (Locally)

Getting the CRUD Out & Submitting Data

AWS - Amazon Web Services

NPM - Node Package Manager

ENV - Environment Variables

SDK - Software Developer Kit

Create Todo (Due by EOD 😂)

Debugging - For Frictionless Feedback Loops

Publishing

Next Steps - This is only the beginning

Kyle Mitofsky

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