What is PocketMocker?

PocketMocker is an in-page HTTP controller for frontend development.

In simple terms, it lets you decide what your API responses should be—without touching the backend or setting up a mock server.

It provides a visual control panel directly in your browser to intercept, override, and manipulate HTTP responses, helping you build robust UIs faster by seeing changes instantly.

Why PocketMocker?

Mock Effortlessly

Stop writing mock code. Intercept requests automatically, generate smart data, import API docs with one click.

Control Completely

• Timing: Simulate network latency, race conditions
• Status: Force 500 errors, 401 unauthorized, empty responses
• Payload: Test edge cases and exception scenarios

Debug Instantly

Edit responses directly in your browser and see UI updates instantly. No tool switching, stay in the flow.

Real-World Use Cases

Instant State Switching

Toggle between Success, Error (500/404), or Empty Data states in one click. verify how your UI handles loading spinners or error toasts without changing a single line of code.

On-the-fly Data Tweaking

Need to test a long username? A missing avatar? Or a specific price format? Just edit the response JSON directly in the panel and see the UI update instantly.

Edge Case Verification

Simulate network delays (latency), timeout errors, or unauthorized (401) responses to ensure your application handles exceptions gracefully.

https://github.com/user-attachments/assets/e7501191-7ef1-4bd4-bd21-6500585fe4ad

Installation

npm install pocket-mocker --save-dev
# or
yarn add pocket-mocker -D
# or
pnpm add pocket-mocker -D

Quick Start

Method 1: Zero Configuration (Local Mode)

Perfect for individual development or quick experimentation. Simply import and start in your project's entry file:

import { pocketMock } from 'pocket-mocker';

// Only start in development environment
if (process.env.NODE_ENV === 'development') {
  pocketMock();
}

After starting your project, you'll see the PocketMock floating panel in the bottom-right corner.

Method 2: Team Collaboration Mode (Vite Plugin) 🔥 Recommended

Ideal for production-level projects. The Vite plugin integrates with the file system, saving Mock rules to config files for team sharing.

1. Import and start in your project's entry file:

import { pocketMock } from 'pocket-mocker';

if (process.env.NODE_ENV === 'development') {
  pocketMock();
}

2. Configure vite.config.ts

import { defineConfig } from 'vite';
import pocketMockPlugin from 'pocket-mocker/vite-plugin';

export default defineConfig({
  plugins: [
    pocketMockPlugin()
  ]
});

3. Start Development

Run npm run dev. PocketMock automatically detects the plugin environment and switches to Server Mode.

Advanced Features

URL Pattern Matching

PocketMock supports powerful URL patterns to mock complex APIs:

• Path Parameters: /api/users/:id → matches /api/users/123, /api/users/john
• Wildcards: /api/* → matches /api/users, /api/users/123/posts
• Mixed Patterns: /api/:version/users/*/profile → matches /api/v1/users/123/profile

Access captured parameters in mock functions:

(req) => {
  const { id, version } = req.params;
  const { include } = req.query;
  return { id: parseInt(id), version, includeAuthor: include === 'true' };
}

Smart Mock Data Generation

PocketMock includes a powerful Smart Mock Generator that allows you to create realistic test data with simple template syntax.

Quick Example

{
  "user": {                           // → Generate user data
    "id": "@guid",                   // → "550e8400-e29b-41d4-a716-446655440000"
    "name": "@name",                 // → "John"
    "username": "@username",       // → "brightpanda"
    "email": "@email",               // → "[email protected]"
    "avatar": "@image(100x100)",     // → "https://via.placeholder.com/100x100"
    "age": "@integer(18,60)",       // → 25
    "role": "@pick(admin,user)",     // → "admin"
    "ip": "@ip",                  // → "192.168.1.1"
    "ipv6": "@ip(v6)"                // → "2001:0db8:85a3:0000:0000:8a2e:0370:7334"
  }
}

Common Generators

More Features

{
  "users|5": {            // Generate 5 users
    "id": "@guid",
    "name": "@name"
  },
  "scores|3-5": "@integer(60,100)"  // Generate 3 to 5 scores
}

Dynamic Response (Function Mock)

You are not limited to static JSON. You can write JavaScript functions to generate responses dynamically based on request!

(req) => {
  // Dynamic response based on Query parameters
  if (req.query.id === '1') {
    return { id: 1, name: 'Admin', role: 'admin' };
  }

  // Dynamic response based on Body content
  if (req.body?.type === 'error') {
    return {
      status: 400,
      body: { message: 'Invalid Parameter' }
    };
  }

  // Default response
  return { id: 2, name: 'Guest' };
}

Config Import

Import mock rules directly from popular API documentation formats with auto-conversion.

• Supported Formats: Postman Collection v2.1.0, OpenAPI 3.0 (Swagger)
• Smart Conversion:
  • user_id -> @guid
  • avatar -> @image
  • {{baseUrl}}/users -> /users

How to use: Click the "Import" button in the dashboard header and select your JSON file.

Comprehensive Network Panel

The built-in Network panel logs all network requests (both mocked and real) in real-time, providing powerful debugging capabilities:

• View Details: Click logs to view full Request/Response Body.
• One-Click Mock: Click the "Mock" button on any log to instantly convert a real request into a mock rule.
• Filter: Filter logs by URL, Method, or Mock status.

Technical Architecture

• Monkey Patching: Intercepts requests by overriding window.fetch and extending XMLHttpRequest prototype chain.
• Shadow DOM: Encapsulates debugging UI in Shadow Root for complete style sandboxing.
• Vite Library Mode: Uses Vite's library mode with css: 'injected' strategy to inline all CSS into JS for single-file import experience.

Roadmap

Check out our Roadmap to see what's next for PocketMocker and how you can contribute to its future!

Contributing & Contact

We welcome all contributions to PocketMocker! Whether it's reporting bugs, suggesting new features, improving documentation, or submitting code, your help is greatly appreciated.

Please read our Contribution Guidelines for details on how to get started.

Contact Me

If you have any questions, suggestions, or would like to connect, feel free to reach out:

• Twitter (X): https://x.com/tiancha79267301
• WeChat
  

License

MIT © tianchangNorth