parse FormData

example.js

const expression = {}

expression.header_content_type = header_content_type: /(?<mimetype>(?<mimetype_type>[a-z]+|\*)\/(?<mimetype_subtype>[a-z][a-z0-9]*(?:\-[a-z0-9]+)*|\*))(?:\s*;\s*charset=(?<charset>\S+))?(?:\s*;\s*boundary=(?<boundary>\S+))?/
expression.header_content_type.exec(request.headers['content-type'])

if (method === 'POST' || method === 'PUT' || method === 'PATCH' || method === 'DELETE') {
			let data

			if ((/(?:text|application)\/json/).test(request_contentType.groups.mimetype)) {
					data = JSON.parse(packet.toString('utf8'))
			}
  
			if ((/application\/x-www-form-urlencoded/).test(request_contentType.groups.mimetype)) {
					data = querystring.parse(packet.toString('utf8'))
			}
  
			if ((/multipart\/form-data/).test(request_contentType.groups.mimetype)) {
					data = dump(from_FormData(request_contentType.groups.boundary, packet.toString('utf8')))
			}
}

libformdata.js

function from_FormData (boundary, data) {
	const indexes = getIndexes(boundary, data)
	const boundaries = getBoundaries(boundary, data, ...indexes)

	return dump(getFormData(...boundaries))

	function dump (them) {
		if (them instanceof Set) {
			const array = []
			for (const each of them)
				each.push(dump(each))
			return array
		}

		if (them instanceof Map) {
			const object = {}
			for (const [k, v] of them)
				object[k] = dump(v)
			return object
		}

		return them
	}

	function * getIndexes (subject, content) {
		for (let index = 0; (index = content.indexOf(subject, index)) !== -1; index += subject.length)
			yield index
	}

	function * getBoundaries (boundary, data, ...indexes) {
		for (let i = 0; i < indexes.length - 1; i++) {
			const bounds = [indexes[i] + boundary.length, indexes[i + 1]]
			const content = data.substring(...bounds)
			yield content
		}
	}

	function getFormData (...boundaries) {
		const expression = {}
		expression.contentDisposition = /Content-Disposition:\s*(inline|attachment|form-data)(?:\s*\;\s*name="([^"]+)")?(?:\s*\;\s*filename\*?="([^"]+)")?(\r\n){2}/
		expression.contentBody = /^([\s\S]+)\r\n$/

		const formData = new Map

		for (const boundary of boundaries) {
			const contentDispositionPattern = expression.contentDisposition.exec(boundary)
			if (!contentDispositionPattern) return {boundary, error: 'Could not find appropriate `Content-Disposition` header'}

			const contentBodyPattern = boundary.substring(contentDispositionPattern.index + contentDispositionPattern[0].length)

			const contentDisposition = contentDispositionPattern[1]
			const name = contentDispositionPattern[2]
			const filename = contentDispositionPattern[3]
			const contentBodyIndex2 = contentBodyPattern.lastIndexOf('\r\n')
			const contentBody = contentBodyPattern.substring(0, contentBodyIndex2)
			const submission = filename ? { filename, contentBody } : contentBody

			if (formData.has(name)) {
				if (formData.get(name) instanceof Set) {
					formData.get(name).add(submission)
				} else {
					formData.set(name, new Set([formData.get(name), submission]))
				}
			} else {
				formData.set(name, submission)
			}
		}

		return formData
	}
}