multipart-poster

Node utility to easily POST multipart forms, including files.

Yes, you could use request for the same purpose, but it's verbose and has some gotchas. We take the pain out of posting multipart forms by automatically converting Booleans, adding brackets to array parameter names (by default), creating read streams for files, and jumping through all the hoops in the right order to get your form data and files successfully sent.

Usage

var MultipartPoster = require("multipart-poster")

This gives you a class. You can construct instances of it that may behave differently from each other. To be more terse, call static methods MultipartPoster.addFile and MultipartPoster.post.

Examples

Upload a cat picture

var url = "http://example.com/kitten-image-uploads"

MultipartPoster.addFile("kittenImage", "Mittens-first-hairball.gif").post(url)

Explore new foods

MultipartPoster
.post("http://example.com/food-suggestions", {
  dishesILike: ["Potatoes Au Gratin", "Yogurt and Honey", "Ice Cream Sandwich"],
  vegan: false,
  vegetarian: true
}, function (error, response, body) {
  console.log( "More foods I might like to try:", body.toString("utf8") )
})

Apply for a high-powered job

var url = "https://example.com/job-applications"
var formData = {
  positionDesired: "emperor",
  firstName: "Marcus",
  lastName: "Aurelius",
  phoneNumber: "N/A",
  emailAddress: "N/A",
  preferredMethodsOfContact: "ouija board, spiritual medium",
  expectedCompensation: "human souls"
}
var poster = new MultipartPoster()
var postRequest

poster
  .addFile("resume", "My Resume.docx")
  .addFile("coverLetter", "why choose an undead emperor.txt")
  .addFile("recommendations", "Hierocles-rec.txt", "Fronto-rec.rtf", "Cassius Dio-rec.md")
postRequest = poster.post(url, formData)
postRequest.on("response", function (response) {
  console.log("Job application upload response status: ", response.statusCode)
})

MultipartPoster methods

addFile

Adds any number of files you want, all with the same parameter name, which you specify as the first argument.

Returns a MultipartPoster instance for method chaining.

var poster1 = new MultipartPoster()

poster1
  .addFile(parameterName, filePath1 [, filePath2 [...]])
  .addFile(anotherParameterName, anotherFilePath)

or

var poster2 = MultipartPoster.addFile(/* same argument signatures */)

post

Send some data somewhere, and return the request object, which is a stream that's returned by the request utility.

Has two argument signatures.

var poster1 = new MultipartPoster()
var poster2 = new MultipartPoster()

poster1.post(url [, formData [, responseHandler [, requestOptions]]])
poster2.post(url [, responseHandler [, requestOptions]])

or

MultipartPoster.post(/* same argument signatures */)

Arguments:

url

(required)

The destination for your data.

formData

(optional)

A plain old JavaScript object. Its key/value pairs become the POST parameter names/values, respectively. Values could be strings, numbers, Booleans, arrays.

If you are only sending files, and have used .addFile previously, then you do not need to specify formData.

Should you want to use formData to send files, then make the value of each POST parameter that's a file a stream.Readable, e.g. via fs.createReadStream("path/to/file.whatever")

If you need more control over form data, then create this object the way the request module expects.

responseHandler

(optional)

A function to call upon receiving a response. It will be called asynchronously, and passed three arguments in this order: error, response, body. If error isn't null, something went wrong. response is the response object, and body is everything following the response headers, as a Buffer by default because null is the default encoding in requestOptions, below.

requestOptions

(optional)

Options as specified in the request documentation.

Defaults to:

{ encoding: null, method: "POST" }

send

An alias for post purely for semantics, in case you want to PUT your form instead of POSTing it.

var putter = new MultipartPoster()

putter.requestOptions.method = "PUT"
putter.send(/* same request signature as post */)

MultipartPoster instance properties

error

Should be null unless something went wrong. Then it may store a meaningful message if our code was able to detect the problem.

parameterOptions

Inherits initial properties from the class-level at MultipartPoster.parameterOptions. You can override them at the instance-level.

See Technical Stuff below for more detail.

requestOptions

Same as the requestOptions argument to the post method.

files

Calls to addFile populate this object, but you can change it manually too. It's a plain old JavaScript object that could look like

{
  parameterName1: filePath,
  parameterName2: [filePath1, filePath2, ...],
  ...
}

Technical Stuff

Array parameters

Some applications expect a POST parameter with an array of values to look like:

colors=blue&colors=red&colors=purple

While others expect:

colors[]=blue&colors[]=red&colors[]=purple

We default to the latter, with brackets. Should you want to change that, turn off the bracketArrayParameterNames parameter option, like so:

  var formData = { colors: ["red", "blue", "purple"] }
  var poster = new MultipartPoster()

  poster.parameterOptions.bracketArrayParameterNames = false
  poster.post(/* ... */)

The above will only affect that one instance, poster. To change this setting for every MultipartPoster, change the setting at the class-level.

MultipartPoster.parameterOptions.bracketArrayParameterNames = false

Undefined and Null form parameters

If you try to post parameters with values that are null or undefined then MultipartPoster will throw an error by default. To change that behavior, choose how you want parameters like that to be converted. For instance, if you want undefined values to be posted as blank strings, then write:

MultipartPoster.parameterOptions.handleUndefined = MultipartPoster.symbols.BLANK_STRING

Should you want parameters with null values to not be sent at all, then do this:

MultipartPoster.parameterOptions.handleNull = MultipartPoster.symbols.SKIP

Boolean form parameters

To have true and false parameter values converted to 1 and 0 respectively:

MultipartPoster.parameterOptions.handleBoolean = MultipartPoster.symbols.BINARY

Parameter conversion

Your parameter conversion behavior options within the MultipartPoster.symbols namespace are: THROW_ERROR, BLANK_STRING, NULL_STRING, BOOLEAN_STRING, BINARY, SKIP.

Class vs. Instance level

These settings will affect how every MultipartPoster instance will behave. For more granular control, construct an instance and set its parameter options to override those taken from the class-level.

In this example, we regress to the behavior exhibited by the request module when encountering a Boolean parameter value.

var poster = new MultipartPoster()

poster.parameterOptions.handleBoolean = MultipartPoster.symbols.THROW_ERROR
poster.post(/* ... */)

Test Specifications

• Post strings and numbers (as strings) from a MultipartPoster instance.
• Post from a static method for convenience.
• Post strings and files.
• Post a file without directly specifying to create a read stream.
• Only post a file.
• Return a stream when posting.
• Convert boolean parameter values to strings by default.
• Post simple arrays.
• Post simple arrays without brackets after parameter names, if desired.
• Post files in an array.
• Post files in an array via one call to the addFile method.
• Post files in an array via multiple calls to the addFile method.
• Handle Boolean values in formData as specified by the user.
• Throw an error if desired when encountering a Boolean parameter.
• Handle null values in formData as specified by the user.
• Throw an error if desired when encountering a null parameter.
• Handle undefined values in formData as specified by the user.
• Throw an error if desired when encountering an undefined parameter.
• Allow you to specify a method other than POST.
• PUT strings and files via the .send alias for .post, for semantics.