Parses HTTP header based on format of RFC-9110

parseHttpHeader.test.ts

import parseHttpHeader from "./parseHttpHeader"

describe("functions/parseHttpHeader", function () {
  it.each([
    [
      "users=0-10/100",
      {
        users: "0-10/100",
      },
    ],
    [
      "next=nextCursor=, prev=prevCursor=",
      {
        prev: "prevCursor=",
        next: "nextCursor=",
      },
    ],
    [
      "</api/3>; rel=next, </api/1>; rel=prev",
      [
        {
          $: "</api/3>",
          rel: "next",
        },
        {
          $: "</api/1>",
          rel: "prev",
        },
      ],
    ],
    [
      "text/html, application/xhtml+xml, application/xml;q=0.9",
      [
        "text/html",
        "application/xhtml+xml",
        {
          $: "application/xml",
          q: "0.9",
        },
      ],
    ],
  ])("%s, %j", function (value, expected) {
    expect(parseHttpHeader(value)).toEqual(expected)
  })
})

parseHttpHeader.ts

/**
 * Parses HTTP header based on format of RFC-9110
 *
 *  Range: users=0-10/100
 *  Link: </api/3>; rel=next, </api/1>; rel=prev
 *  Accept: text/html, application/xhtml+xml, application/xml;q=0.9
 *
 * @param header string
 * @return
 */
const parseHttpHeader = (header: string) => {
  const values = header.split(",").map((value) => {
    const parts = value.trim().split(/;/)

    if (parts.length == 1 && !value.includes("=")) {
      return parts[0].trim()
    } else {
      const params: Record<string, string | null> = {}
      parts.forEach((value) => {
        const index = value.indexOf("=")
        const parsed =
          index > 0 ? [value.slice(0, index), value.slice(index + 1)] : [value]
        if (parsed[1]) {
          params[parsed[0].trim()] = parsed[1].trim()
        } else {
          params["$"] = parsed[0].trim()
        }
      })
      return params
    }
  })

  return values.length == 1
    ? values[0]
    : values.every(
        (v) =>
          typeof v === "object" && Object.keys(v).length === 1 && !("$" in v),
      )
    ? values.reduce((o, i) => Object.assign(o, i), {})
    : values
}

export default parseHttpHeader