Middleware Pipeline

mediumcodingJavaScriptDesign PatternsFunctions~25 min

Asked at Vercel, Stripe, Shopify

Overview

Implement createPipeline(middlewares) that returns an async function processing a context through each middleware sequentially.

Each middleware has the signature (ctx, next) => {} — must call next() to continue.

Examples

const pipeline = createPipeline([
  async (ctx, next) => { ctx.x = 1; await next(); },
  async (ctx, next) => { ctx.y = 2; await next(); },
]);
const ctx = {};
await pipeline(ctx); // ctx = { x: 1, y: 2 }

Solution

Reveal solution

function createPipeline(middlewares) {
  return async function(ctx) {
    let index = 0;
    async function next() {
      if (index < middlewares.length) {
        const mw = middlewares[index++];
        await mw(ctx, next);
      }
    }
    await next();
    return ctx;
  };
}

middleware-pipeline.js

Middleware Pipeline

mediumcodingJavaScriptDesign Patterns

Overview

Implement createPipeline(middlewares) that returns an async function processing a context through each middleware sequentially.

Each middleware has the signature (ctx, next) => {} — must call next() to continue.

Examples

const pipeline = createPipeline([
  async (ctx, next) => { ctx.x = 1; await next(); },
  async (ctx, next) => { ctx.y = 2; await next(); },
]);
const ctx = {};
await pipeline(ctx); // ctx = { x: 1, y: 2 }

Solution

Reveal solution

function createPipeline(middlewares) {
  return async function(ctx) {
    let index = 0;
    async function next() {
      if (index < middlewares.length) {
        const mw = middlewares[index++];
        await mw(ctx, next);
      }
    }
    await next();
    return ctx;
  };
}

NameTopicDifficulty

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