Mime Message Composer

Mime / Multipart message composer is a package that helps to encode the request body in a multipart message format. This composer helps to create the multipart encoded body like multipart/alternative.

Install using NPM

npm i mime_message_composer

Info

This package works on a concept of content type. Every mutipart message hava a content type that describe what content it holds.
This package exposes two classes:

• BranchableCT (Branchable Content Type)
  BranchableCT are those content type which have its boundary defined and will have multiple child content types within itself.
  Example of BranchableCT are: multipart/alternative, multipart/mixed, and others
• BodyCT (Body Content Type)
  BodyCT are those content type which contains body/value in as its body with required headers and cannot have additional content types in its body.
  Example of BodyCT are: text/plain, application/json, and others

Docs

BranchableCT

• Constructor:

BranchableCT(ContentType:String, Boundary:String) - E.g: BranchableCT("multipart/alternative","alt_part1")

• Methods:

appendHeaders(headers: HeaderType[]):this - E.g appendHeaders([{name:"Content-Transfer-Encoding",value:"base64"}])

- HeaderType is a Object that has name and value property.
- Used to add headers to the content type.

addBranches(branches: ContentTypeI[]):this - E.g: addBranches([new BranchableCT(..), new BodyCT(..)])

- Add subBranch of this content type
- Both Branchable and Body Interface implements ContentTypeI.

compile():string - E.g: compile()

- Generate the compiled Mime message of this content type by combining with headers and branches.

BodyCT

• Constructor:

BodyCT(ContentType:String, additionalCT: HeaderType) - E.g BodyCT("application/json",{name:"name",value:"package.json"})

• Methods:

appendHeaders(headers: HeaderType[]):this - E.g appendHeaders([{name:"Content-Transfer-Encoding",value:"base64"}])

- HeaderType is a Object that has name and value property.
- Used to add headers to the content type.

getBody():string - eg getBody()

- Get Body data added to this content type class

setBody(data: string):this - E.g: setBody("any data depending on headers")

- Add body data to the content type.

compile():string - E.g: compile()

- Generate the compiled Mime message of this content type by combining with headers and branches.

Usage

const textPlain = new BodyCT({
  contentType: "text/plain",
  additionalCT: {
    name: "charset",
    value: "UTF-8"
 }
}).appendHeaders([
  {
    name: "Content-Transfer-Encoding",
    value: "7bit"
  }
]).setBody("this is plain text body");

const textHtml = new BodyCT({
  contentType: "text/html",
  additionalCT: {
    name: "charset",
    value: "UTF-8"
  }
}).appendHeaders([
  {
    name: "Content-Transfer-Encoding",
    value: "7bit"
  }
]).setBody("<b>this is plain text body</b>");

// Base CT
const alternative = new BranchableCT({
  contentType: "multipart/alternative",
  boundary: "foo-bar"
}).appendHeaders([
  {
    name: "From",
    value: "[email protected]"
  },
  {
    name: "To",
    value: "[email protected]"
  },
  {
    name: "Encoding",
    value: "7bit"
  }
]).addBranches([textPlain, textHtml]);

console.log(alternative.compile())

Output:

Content-Type: multipart/alternative; boundary="foo-bar"
From: "[email protected]
To: "[email protected]"
Encoding: 7bit

--foo-bar
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: 7bit

this is plain text body
--foo-bar
Content-Type: text/html; charset="UTF-8"
Content-Transfer-Encoding: 7bit

<b>this is plain text body</b>
--foo-bar--

Links

• RFC1341