karladler / async-busboy

Promise based multipart form parser for KoaJS

Promise Based Multipart Form Parser

The typical use case for this library is when handling forms that contain file upload field(s) mixed with other inputs. Parsing logic relies on busboy. Designed for use with Koa2 and Async/Await.

Examples

Async/Await

import asyncBusboy from 'async-busboy';

// Koa 2 middleware
async function(ctx, next) {
  const {files, fields} = await asyncBusboy(ctx.req);

  // Make some validation on the fields before upload to S3
  if ( checkFiles(fields) ) {
    files.map(uploadFilesToS3)
  } else {
    return 'error';
  }
}

ES5 with promise

var asyncBusboy = require('async-busboy');

function(someHTTPRequest) {
  asyncBusboy(someHTTPRequest).then(function(formData) {
    // do something with formData.files
    // do someting with formData.fields
  });
}

As of today there is no support for directly piping of the request stream into a consumer. The files are first written to disk using os.tmpdir(). When the consumer stream drained the request stream, files will be automatically removed, otherwise the host OS should take care of the cleaning process.

Working with nested inputs and objects

Make sure to serialize objects before sending them as formData. i.e:

// Given an object that represent the form data:
{
  'field1': 'value',
  'objectField': {
    'key': 'anotherValue'
  },
  'arrayField': ['a', 'b']
  //...
};

Should be sent as:

// -> field1[value]
// -> objectField[key][anotherKey]
// -> arrayField[0]['a']
// -> arrayField[1]['b']
// .....

Here is a function that can take care of this process

const serializeFormData = (obj, formDataObj, namespace = null) => {
  var formDataObj = formDataObj || {};
  var formKey;
  for(var property in obj) {
    if(obj.hasOwnProperty(property)) {
      if(namespace) {
        formKey = namespace + '[' + property + ']';
      } else {
        formKey = property;
      }

      var value = obj[property];
      if(typeof value === 'object' && !(value instanceof File) && !(value instanceof Date)) {
          serializeFormData(value, formDataObj, formKey);
      } else if(value instanceof Date) {
        formDataObj[formKey] = value.toISOString();
      } else {
        formDataObj[formKey] = value;
      }
    }
  }
  return formDataObj;
};

// -->

Try it on your local

If you want to run some test localy, clone this repo, then run: node examples/index.js From there you can use something like Postman to send POST request to localhost:8080. Note: When using Postman make sure to not send a Content-Type header, if it's filed by default, just delete it. (This is to let the boudary header be generated automaticaly)

Use cases:

• Form sending only octet-stream (files)

• Form sending file octet-stream (files) and input fields. a. File and fields are processed has they arrive. Their order do not matter. b. Fields must be processed (for example validated) before processing the files.