Try Mimlet in your browser

Edit a small program and run it on this page, with nothing to install. The code runs locally in your browser. Nothing you type is sent to a server or saved.

Mimlet is in beta (0.1.0-beta.3), so APIs can still change before a stable release. If something is confusing, send beta feedback.

Example Zod: build and validateNamed setters with fluent()Connected scenario: customer, order, linesValibot adapter Time limit 2 seconds 5 seconds 10 seconds

fromZod(...).with(...).buildValidated(). The last line breaks the schema on purpose, so you can see a validation error and its path. Zod and ArkType guide

Code

import { z } from 'zod';
import { fromZod } from '@mimlet/zod';

const User = z.object({
  name: z.string().min(1),
  email: z.email(),
  age: z.number().int().min(18).max(99),
});

const users = fromZod(User);

// Set the fields your test cares about. Mimlet generates the rest from
// the schema, and buildValidated() checks the result with Zod.
console.log(users.with({ name: 'Ada' }).buildValidated());

// This age breaks the schema, so the run ends with a validation error
// that names the field. Change 12 to 42 and run it again.
console.log(users.with({ age: 12 }).buildValidated());
 

import { z } from 'zod'; import { fromZod } from '@mimlet/zod'; const User = z.object({ name: z.string().min(1), email: z.email(), age: z.number().int().min(18).max(99), }); const users = fromZod(User); // Set the fields your test cares about. Mimlet generates the rest from // the schema, and buildValidated() checks the result with Zod. console.log(users.with({ name: 'Ada' }).buildValidated()); // This age breaks the schema, so the run ends with a validation error // that names the field. Change 12 to 42 and run it again. console.log(users.with({ age: 12 }).buildValidated());

JavaScript, with imports from @mimlet/core, @mimlet/zod, @mimlet/valibot, @mimlet/json-schema, zod, valibot. Press Ctrl+Enter or Cmd+Enter to run, and Escape to stop. Tab moves to the next control.

Choose an example, edit it if you like, then run it.

Output

Run the example to see its output here.

What you can run

Each example is a short JavaScript program with ES module imports. It can import from:

• @mimlet/core, for builders, fluent(), scenarios and sessions
• @mimlet/zod, with zod 4.6.5
• @mimlet/valibot, with valibot 1.5.0
• @mimlet/json-schema

The Mimlet packages are built from the same revision of this repository as the site you are reading. The vendor libraries are pinned to the versions above.

Output shows what the program passes to console.log() and the values it exports. When the program throws, the sandbox shows the error. For a validation error from buildValidated(), it lists each issue with the path of the field that failed, such as age or address.postcode.

The sandbox runs JavaScript, not TypeScript. Remove type annotations when you paste code from the guides. Put imports at the top of the program.

How it runs

• The first time you press Run, the page downloads the sandbox runtime: the packages and libraries above, bundled into one file. Other pages never load it.
• Each run starts in a new hidden frame that has its own empty origin. The program runs in a Web Worker inside that frame. It cannot read or change this page, its cookies or the site's storage.
• The frame's Content Security Policy blocks network requests and scripts from anywhere else, so the program cannot send data out of your browser.
• Each run has a time limit of 2, 5 or 10 seconds. Stop, Escape or the time limit ends the run straight away, even in the middle of a loop. Chromium-based browsers can take up to two more seconds to release the processor.
• Output is limited to 500 console entries. Memory is not limited beyond what your browser allows, so a program that allocates a lot can slow down or close the tab.
• Edits stay in the page while it is open. Reloading the page restores the examples.

Use it in a project

Install the beta packages you need, then continue with Getting started, named setters or correlated scenarios.

npm install --save-dev @mimlet/zod@0.1.0-beta.3 zod@4.6.5

For JSON Schema documents on your own machine, the local schema playground generates fixtures without a network connection.