headers-polyfill/src/transformers/stringToHeaders.ts

A native "Headers" class polyfill.

import { Headers } from '../Headers'

/**
 * Converts a string representation of headers (i.e. from XMLHttpRequest)
 * to a new `Headers` instance.
 */
export function stringToHeaders(str: string): Headers {
  const lines = str.trim().split(/[\r\n]+/)

  return lines.reduce((headers, line) => {
    if (line.trim() === '') {
      return headers
    }

    const parts = line.split(': ')
    const name = parts.shift()
    const value = parts.join(': ')
    headers.append(name, value)

    return headers
  }, new Headers())
}