insomnia/packages/insomnia-app/app/network/basic-auth/get-header.js

// @flow

import type {RequestHeader} from '../../models/request';

export function getBasicAuthHeader (username: ?string, password: ?string): RequestHeader {
  const name = 'Authorization';
  const header = `${username || ''}:${password || ''}`;
  const authString = Buffer.from(header, 'utf8').toString('base64');
  const value = `Basic ${authString}`;
  return {name, value};
}