State Management

Byte has built-in mechanism for creating and managing states during requests.

To attach a state to the ctx object, call app.set with the state name and a handler that returns the initial state value:

app.set('startTime', performance.now);

// Is the same as
app.prepare((ctx) => {
   ctx.startTime = performance.now();
});

And use it in other middlewares or handlers (chaining is required):

app
  // Attach 'startTime' property to the context on every request
  .set('startTime', performance.now)
  // Example middleware
  .prepare(cors())
  // Log the time it takes to run the CORS middleware
  .prepare((ctx) => {
    console.log(performance.now() - ctx.startTime);
  });

The handler passed in app.set should be asynchronous if it returns a Promise.

Because calling app.set is the same as registering a middleware, the following example will not work:

app
  .prepare((ctx) => {
    // 'ctx.startTime' is undefined, so this logs NaN
    console.log(performance.now() - ctx.startTime);
  })
  .set('startTime', performance.now);

Validation

You can validate the state value before attaching to ctx using app.state.

// My optimization trick
const noop = () => null;

app.state('message', async (ctx) => {
  const message = await ctx.req.text().catch(noop);

  // Return an empty response with status 403
  // if body parsing failed or message length is larger than 70
  if (message === null || message.length > 70) {
    ctx.status = 403;
    return ctx.end();
  }

  // Attach to `ctx` to use later
  return message;
});