Define your own mime tree, no magic included
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README.md

emailjs-mime-builder

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emailjs-mime-builder is a low level rfc2822 message composer. Define your own mime tree, no magic included.

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Usage

Install via

    npm install --save emailjs-mime-builder

... and then use via

import MimeBuilder from 'emailjs-mime-builder'

Create a new MimeBuilder object with

var builder = new MimeBuilder(contentType [, options]);

Where

  • contentType - define the content type for created node. Can be left blank for attachments (content type derived from filename option if available)
  • options - an optional options object
    • filename - String filename for an attachment node
    • baseBoundary - String shared part of the unique multipart boundary (generated randomly if not set)

Methods

The same methods apply to the root node created with new MimeBuilder() and to any child nodes.

createChild

Creates and appends a child node to the node object

node.createChild(contentType, options)

The same arguments apply as with new MimeBuilder(). Created node object is returned.

Example

new MimeBuilder("multipart/mixed").
    createChild("multipart/related").
        createChild("text/plain");

Generates the following mime tree:

multipart/mixed
  ↳ multipart/related
      ↳ text/plain

appendChild

Appends an existing child node to the node object. Removes the node from an existing tree if needed.

node.appendChild(childNode)

Where

  • childNode - child node to be appended

Method returns appended child node.

Example

var childNode = new MimeBuilder("text/plain"),
    rootNode = new MimeBuilder("multipart/mixed");
rootnode.appendChild(childNode);

Generates the following mime tree:

multipart/mixed
  ↳ text/plain

replace

Replaces current node with another node

node.replace(replacementNode)

Where

  • replacementNode - node to replace the current node with

Method returns replacement node.

Example

var rootNode = new MimeBuilder("multipart/mixed"),
    childNode = rootNode.createChild("text/plain");
childNode.replace(new MimeBuilder("text/html"));

Generates the following mime tree:

multipart/mixed
  ↳ text/html

remove

Removes current node from the mime tree. Does not make a lot of sense for a root node.

node.remove();

Method returns removed node.

Example

var rootNode = new MimeBuilder("multipart/mixed"),
    childNode = rootNode.createChild("text/plain");
childNode.remove();

Generates the following mime tree:

multipart/mixed

setHeader

Sets a header value. If the value for selected key exists, it is overwritten.

You can set multiple values as well by using [{key:"", value:""}] or {key: "value"} structures as the first argument.

node.setHeader(key, value);

Where

  • key - String|Array|Object Header key or a list of key value pairs
  • value - String Header value

Method returns current node.

Example

new MimeBuilder("text/plain").
    setHeader("content-disposition", "inline").
    setHeader({
        "content-transfer-encoding": "7bit"
    }).
    setHeader([
        {key: "message-id", value: "abcde"}
    ]);

Generates the following header:

Content-type: text/plain
Content-Disposition: inline
Content-Transfer-Encoding: 7bit
Message-Id: <abcde>

addHeader

Adds a header value. If the value for selected key exists, the value is appended as a new field and old one is not touched.

You can set multiple values as well by using [{key:"", value:""}] or {key: "value"} structures as the first argument.

node.addHeader(key, value);

Where

  • key - String|Array|Object Header key or a list of key value pairs
  • value - String Header value

Method returns current node.

Example

new MimeBuilder("text/plain").
    addHeader("X-Spam", "1").
    setHeader({
        "x-spam": "2"
    }).
    setHeader([
        {key: "x-spam", value: "3"}
    ]);

Generates the following header:

Content-type: text/plain
X-Spam: 1
X-Spam: 2
X-Spam: 3

getHeader

Retrieves the first mathcing value of a selected key

node.getHeader(key)

Where

  • key - String Key to search for

Example

new MimeBuilder("text/plain").getHeader("content-type"); // text/plain

setContent

Sets body content for current node. If the value is a string, charset is added automatically to Content-Type (if it is text/*). If the value is a Typed Array, you need to specify the charset yourself.

node.setContent(body)

Where

  • body - String|Uint8Array body content

Example

new MimeBuilder("text/plain").setContent("Hello world!");

build

Builds the rfc2822 message from the current node. If this is a root node, mandatory header fields are set if missing (Date, Message-Id, MIME-Version)

node.build()

Method returns the rfc2822 message as a string

Example

new MimeBuilder("text/plain").setContent("Hello world!").build();

Returns the following string:

Content-type: text/plain
Date: <current datetime>
Message-Id: <generated value>
MIME-Version: 1.0

Hello world!

getEnvelope

Generates a SMTP envelope object. Makes sense only for root node.

var envelope = node.generateEnvelope()

Method returns the envelope in the form of {from:'address', to: ['addresses']}

Example

new MimeBuilder().
    addHeader({
        from: "From <from@example.com>",
        to: "receiver1@example.com",
        cc: "receiver2@example.com"
    }).
    getEnvelope();

Returns the following object:

{
    "from": "from@example.com",
    "to": ["receiver1@example.com", "receiver2@example.com"]
}

Notes

Addresses

When setting address headers (From, To, Cc, Bcc) use of unicode is allowed. If needed the addresses are converted to punycode automatically.

Attachments

For attachments you should minimally set filename option and Content-Disposition header. If filename is specified, you can leave content type blank - if content type is not set, it is detected from the filename.

new MimeBuilder("multipart/mixed").
  createChild(false, {filename: "image.png"}).
  setHeader("Content-Disposition", "attachment");

Obviously you might want to add Content-Id header as well if you want to reference this attachment from the HTML content.

MIME structure

Most probably you only need to deal with the following multipart types when generating messages:

  • multipart/alternative - includes the same content in different forms (usually text/plain + text/html)
  • multipart/related - includes main node and related nodes (eg. text/html + referenced attachments)
  • multipart/mixed - includes other multipart nodes and attachments, or single content node and attachments

Examples

One content node and an attachment

multipart/mixed
  ↳ text/plain
  ↳ image/png

Content node with referenced attachment (eg. image with Content-Type referenced by cid: url in the HTML)

multipart/related
  ↳ text/html
  ↳ image/png

Plaintext and HTML alternatives

multipart/alternative
  ↳ text/html
  ↳ text/plain

One content node with referenced attachment and a regular attachment

multipart/mixed
  ↳ multipart/related
    ↳ text/plain
    ↳ image/png
  ↳ application/x-zip

Alternative content with referenced attachment for HTML and a regular attachment

multipart/mixed
  ↳ multipart/alternative
    ↳ text/plain
    ↳ multipart/related
      ↳ text/html
      ↳ image/png
  ↳ application/x-zip

Get your hands dirty

git clone git@github.com:whiteout-io/mailbuild.git
cd mailbuild
npm install && npm test
grunt dev
go to http://localhost:12345/example/ to run the example
go to http://localhost:12345/test/ to run the tests in your browser of choice

License

Copyright (c) 2013 Andris Reinman

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in
all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
THE SOFTWARE.