9
3

Delete article

Deleted articles cannot be recovered.

Draft of this article would be also deleted.

Are you sure you want to delete this article?

More than 3 years have passed since last update.

Nodeでmultipart/form-dataを送る

Last updated at Posted at 2020-04-03

form-data を使う。

form-data/form-data: A module to create readable "multipart/form-data" streams. Can be used to submit forms and file uploads to other web applications.

Axios

const axios = require("axios");
const FormData = require("form-data");

const form = new FormData();
form.append("message", "hello");

const res = await axios.post(API, form, {
  headers: form.getHeaders()
});

node-fetch

const fetch = require("node-fetch");
const FormData = require("form-data");

const form = new FormData();
form.append("message", "helllo");

const res = await fetch(API, {
  method: "POST",
  body: form
});

なぜ node-fetch はヘッダーでgetHeaders()を利用しなくていいのか?

理由は単純で、form-dataを特別に扱っている。
https://github.com/node-fetch/node-fetch/blob/c167190c6ee21234ba41bd8430700d4720bf64ce/src/body.js#L320-L323

	// Detect form data input from form-data module
	if (body && typeof body.getBoundary === 'function') {
		return `multipart/form-data;boundary=${body.getBoundary()}`;
	}

さて、multipart/form-data;はいいにしても、boundaryとはなんだろうか。
boundaryとは、複数の情報を続けて送る際、データの仕切り線の役割を果たす。
form-dataの実装を見ると、-が26文字、ランダムな数値が24字の50文字の仕切り線を生成する。

FormData.prototype._generateBoundary = function() {
  // This generates a 50 character boundary similar to those used by Firefox.
  // They are optimized for boyer-moore parsing.
  var boundary = '--------------------------';
  for (var i = 0; i < 24; i++) {
    boundary += Math.floor(Math.random() * 10).toString(16);
  }

  this._boundary = boundary;
};

これに\r\nを付加したものを区切りにする。
詳しくは、以下の記事に詳しい。

いまさら聞けないHTTPマルチパートフォームデータ送信 - SATOXのシテオク日記

9
3
0

Register as a new user and use Qiita more conveniently

  1. You get articles that match your needs
  2. You can efficiently read back useful information
  3. You can use dark theme
What you can do with signing up
9
3

Delete article

Deleted articles cannot be recovered.

Draft of this article would be also deleted.

Are you sure you want to delete this article?