Introduction to Co-Body

Co-Body is a flexible and efficient middleware parser used in conjunction with Koa, a progressive Node.js framework for building web applications and APIs. Co-Body supports various content types such as JSON, form-urlencoded, and text. This article provides a comprehensive overview of the Co-Body APIs and demonstrates how to utilize them in a Koa application.

Installing Co-Body

npm install co-body

Basic Usage

  const koa = require('koa');
  const app = new koa();
  const coBody = require('co-body');

  app.use(async (ctx, next) => {
    const body = await coBody(ctx);
    ctx.body = `Request Body: ${JSON.stringify(body)}`;
    await next();
  });

  app.listen(3000, () => {
    console.log('Server started on port 3000');
  });

Parsing JSON

  app.use(async (ctx, next) => {
    const body = await coBody.json(ctx);
    ctx.body = `JSON Body: ${JSON.stringify(body)}`;
    await next();
  });

Parsing URL-encoded Form Data

  app.use(async (ctx, next) => {
    const body = await coBody.form(ctx);
    ctx.body = `Form Body: ${JSON.stringify(body)}`;
    await next();
  });

Parsing Text

  app.use(async (ctx, next) => {
    const body = await coBody.text(ctx);
    ctx.body = `Text Body: ${body}`;
    await next();
  });

Combining Parsers

  app.use(async (ctx, next) => {
    try {
      const body = await Promise.any([
        coBody.json(ctx),
        coBody.form(ctx),
        coBody.text(ctx)
      ]);
      ctx.body = `Parsed Body: ${JSON.stringify(body)}`;
    } catch (err) {
      ctx.throw(400, 'Unsupported body format');
    }
    await next();
  });

Error Handling

  app.use(async (ctx, next) => {
    try {
      const body = await coBody(ctx);
      ctx.body = `Body: ${JSON.stringify(body)}`;
    } catch (err) {
      ctx.throw(422, 'Body parsing error');
    }
    await next();
  });

Full Application Example

Below is a full example of a Koa application using several Co-Body parsers:

  const koa = require('koa');
  const app = new koa();
  const coBody = require('co-body');

  app.use(async (ctx, next) => {
    try {
      const body = await Promise.any([
        coBody.json(ctx),
        coBody.form(ctx),
        coBody.text(ctx)
      ]);
      ctx.body = `Parsed Body: ${JSON.stringify(body)}`;
    } catch (err) {
      ctx.throw(400, 'Unsupported body format');
    }
    await next();
  });

  app.listen(3000, () => {
    console.log('Server started on port 3000');
  });

By incorporating Co-Body into your Koa applications, you ensure robust and flexible request parsing, which is essential for handling diverse client data submissions efficiently.

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