<p><a href="https://github.com/colinhacks/zod">Zod</a> is the most famous validation library in the TypeScript ecosystem. With Zod, you create a <em>schema</em> and validate your data according to the schema. Observe the schema below:</p>
<pre><code class="highlited-code-wrapper langts"><div class="highlited-code" data-language="ts">import { z } from 'zod'

const UserSchema = z.object({
  name: z.string().min(1),
  age: z.number({ coerce: true }).min(18),
  email: z.string().email(),
})</div>
</code></pre><p>This schema can be used to validate an object as follows:</p>
<pre><code class="highlited-code-wrapper langts"><div class="highlited-code" data-language="ts">const data = {
  name: 'John Doe',
  age: 18,
  email: 'john@example.com',
}

// If there is a validation error, it throws an error
const validatedData = UserSchema.parse(data)

// If there is a validation error, it returns an error object for you to handle later
const safeValidatedData = UserSchema.safeParse(data)
// =&gt; { success: false; error: ZodError }
// =&gt; { success: true; data: 'billie' }</div>
</code></pre><p>Zod is capable of performing various types of validations on your data, so be sure to read the <a href="https://github.com/colinhacks/zod">documentation</a> for more details.</p>
<h2>Validating Environment Variables</h2>
<p>We can use Zod to validate the values present in <a href="https://nodejs.org/api/process.html#processenv"><code>process.env</code></a> and even process them before using the environment variables in our application. Usually, I like to create an <code>environment.ts</code> file, as in the example below:</p>
<pre><code class="highlited-code-wrapper langts"><div class="highlited-code" data-language="ts">import { z } from 'zod'

const environmentSchema = z.object({
  // Define the possible values for NODE_ENV, always leaving a default value:
  NODE_ENV: z.enum(['test', 'development', 'production']).default('production'),
  // Environment variables are always defined as strings. Here, convert the string to a number and set a default value:
  PORT: z.number({ coerce: true }).default(3000),
})

export const env = environmentSchema.parse(process.env)</div>
</code></pre><p>Then, just import the variable and use it throughout my application:</p>
<pre><code class="highlited-code-wrapper langts"><div class="highlited-code" data-language="ts">import Fastify from 'fastify'
import { env } from './environment.js'

const app = Fastify({ logger: true })
app.listen({ port: env.PORT }, (err) =&gt; {
  if (err) {
    app.log.error(err)
    process.exit(1)
  }
})</div>
</code></pre>

Douglas Moura

Douglas Moura

#Zod

Validate your environment variables with Zod