428 Precondition Required

The server requires conditional headers to prevent ‘lost updates’ where two people edit a file at the same time.

When and Why to Use It

Use this to enforce safe collaborative editing. If a client tries to PUT updates to a shared document without specifying which exact version they are modifying, throw a 428 to force them to use safe conditional headers.

Usage Examples

Shokupan (Functional)

import { HttpException, get } from 'shokupan';

export const getResource = get('/resource', () => {
    throw new HttpException('Precondition Required', 428);
});

Shokupan (Controller)

import { Controller, Get, HttpException } from 'shokupan';

@Controller('/api')
export class ExampleController {
    @Get('/resource')
    getResource() {
        throw new HttpException('Precondition Required', 428);
    }
}

Express

import express from 'express';
const app = express();

app.get('/resource', (req, res) => {
    res.status(428).json({ error: 'Precondition Required' });
});

Nest

import { Controller, Get, HttpException } from '@nestjs/common';

@Controller('api')
export class ExampleController {
  @Get('resource')
  getResource() {
    throw new HttpException('Precondition Required', 428);
  }
}

Koa

import Koa from 'koa';
const app = new Koa();

app.use(async ctx => {
  if (ctx.path === '/resource' && ctx.method === 'GET') {
    ctx.status = 428;
    ctx.body = { error: 'Precondition Required' };
  }
});