typescript 47 lines · 8 steps

Validating config with Zod schemas

A Zod schema validates untrusted config at runtime and produces a fully typed, guaranteed-valid object.

Explained by highlit

Zod Intermediate schema-validation runtime-safety type-inference error-reporting

1import { z } from "zod";
2 
3const DatabaseSchema = z.object({
4  host: z.string().min(1),
5  port: z.number().int().min(1).max(65535),
6  ssl: z.boolean().default(false),
7  pool: z.object({
8    min: z.number().int().nonnegative(),
9    max: z.number().int().positive(),
10  }).refine((p) => p.max >= p.min, {
11    message: "max must be >= min",
12    path: ["max"],
13  }),
14});
15 
16const ConfigSchema = z.object({
17  env: z.enum(["development", "staging", "production"]),
18  database: DatabaseSchema,
19  features: z.record(z.string(), z.boolean()).default({}),
20  workers: z.array(z.object({
21    name: z.string(),
22    concurrency: z.number().int().positive(),
23  })).min(1),
24});
25 
26export type Config = z.infer<typeof ConfigSchema>;
27 
28export interface ConfigIssue {
29  path: string;
30  message: string;
31}
32 
33export function loadConfig(raw: unknown): Config {
34  const result = ConfigSchema.safeParse(raw);
35  if (result.success) return result.data;
36 
37  const issues: ConfigIssue[] = result.error.issues.map((issue) => ({
38    path: issue.path.length ? issue.path.join(".") : "<root>",
39    message: issue.message,
40  }));
41 
42  const report = issues
43    .map((i) => `  \u2022 ${i.path}: ${i.message}`)
44    .join("\n");
45 
46  throw new Error(`Invalid configuration:\n${report}`);
47}

01 / 01

STEP 01

Walkthrough

Space play ←→ step click any line

Three takeaways

1Zod schemas double as both runtime validators and the single source of truth for static types.
2refine lets you attach cross-field invariants that simple field types can't express.
3safeParse plus issue mapping turns raw validation failures into readable, actionable error reports.

Related explainers

typescript

import { registerLocaleData } from '@angular/common';
import localeFr from '@angular/common/locales/fr';
import localeFrExtra from '@angular/common/locales/extra/fr';
import localeDe from '@angular/common/locales/de';

Locale-aware bootstrapping in Angular

i18n localization dependency-injection

Intermediate 8 steps

typescript

import { Module } from '@nestjs/common';
import { ConfigModule } from '@nestjs/config';
import * as Joi from 'joi';

Validating env config at boot in NestJS

configuration schema-validation environment-variables

Intermediate 8 steps

typescript

import { Inject, Injectable, Logger } from '@nestjs/common';
import { CACHE_MANAGER } from '@nestjs/cache-manager';
import { Cache } from 'cache-manager';
import { InjectRepository } from '@nestjs/typeorm';

A cache-aside country lookup in NestJS

cache-aside dependency-injection batch-lookup

Intermediate 8 steps

typescript

import { Injectable, effect, signal, computed } from '@angular/core';
 
interface Preferences {
  theme: 'light' | 'dark';

A signal-based preferences store in Angular

signals state-management persistence

Intermediate 7 steps

typescript

import { useEffect, useState } from "react";
 
interface Section {
  id: string;

Building a scroll-spy hook in React

custom-hooks intersectionobserver dom-observation

Intermediate 8 steps

typescript

import { Injectable, Scope, Inject, NotFoundException } from '@nestjs/common';
import { REQUEST } from '@nestjs/core';
import { Request } from 'express';
import { DataSource } from 'typeorm';