Introduction to koa-body

koa-body is a powerful middleware for the Koa framework that helps in handling incoming request data with ease. It supports multiple types of incoming data formats including formdata, JSON, and text. This makes koa-body a versatile tool for developing robust backend applications.

Basic Usage

To get started with koa-body, you need to first install it using npm:

  npm install koa-body

Next, to use koa-body in your Koa application, you can register it as a middleware:

  const Koa = require('koa');
  const koaBody = require('koa-body');
  
  const app = new Koa();
  
  app.use(koaBody());
  
  app.listen(3000, () => {
      console.log('Server is running on port 3000');
  });

API Examples

• Handling Form Data

  You can handle form data by setting multipart: true:

        app.use(koaBody({ multipart: true }));
        
        app.use(ctx => {
            if (ctx.method === 'POST') {
                console.log(ctx.request.body);
            }
        });
      

• Handling JSON Requests

  Set json: true to automatically parse JSON payloads:

        app.use(koaBody({ json: true }));
        
        app.use(ctx => {
            if (ctx.is('json')) {
                console.log(ctx.request.body);
            }
        });
      

• File Uploads

  Using koa-body, you can easily handle file uploads:

        app.use(koaBody({ multipart: true }));
        
        app.use(ctx => {
            const files = ctx.request.files;
            console.log(files);
        });
      

• Limiting Upload Size

  Set a limit on the size of uploads to prevent potential abuse:

        app.use(koaBody({ multipart: true, formidable: { maxFileSize: 200 * 1024 * 1024 }}));
        
        app.use(ctx => {
            const files = ctx.request.files;
            console.log(files);
        });
      

• Handling URL-Encoded Data

  You can also parse URL-encoded data using koa-body:

        app.use(koaBody({ urlencoded: true }));
        
        app.use(ctx => {
            console.log(ctx.request.body);
        });
      

• Combining Middleware

  Here is an example of combining various capabilities of koa-body:

        app.use(koaBody({ multipart: true, urlencoded: true, json: true }));
        
        app.use(ctx => {
            console.log(ctx.request.body);
        });
      

Example Application

Below is an example Koa application demonstrating multiple features of koa-body:

  const Koa = require('koa');
  const koaBody = require('koa-body');
  
  const app = new Koa();
  
  app.use(koaBody({
      multipart: true,
      urlencoded: true,
      json: true,
      formidable: { maxFileSize: 200 * 1024 * 1024 }
  }));
  
  app.use(ctx => {
      if (ctx.method === 'POST') {
          ctx.body = {
              textData: ctx.request.body,
              files: ctx.request.files
          };
      } else {
          ctx.body = 'Send a POST request to see form data and file logs.';
      }
  });
  
  app.listen(3000, () => {
      console.log('Server is running on port 3000');
  });

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