url-join/lib/url-join.js

Join urls and normalize as in path.join.

const SCHEME = '[^/:\\d][^/:]*';
const PLAIN_PROTOCOL = new RegExp('^' + SCHEME + ':/*$');
const PROTOCOL_PREFIX = new RegExp('^(' + SCHEME + '):/*');
const HOST_PORT = /^[^/:]+:\d+(?:[/?#]|$)/;

function normalize (strArray) {
  const resultArray = [];
  // Whether each part in resultArray was separated from the previous one by a slash in the input.
  const slashBefore = [];

  // Filter out any empty string values.
  strArray = strArray.filter((part) => part !== '');
  if (strArray.length === 0) { return ''; }

  if (typeof strArray[0] !== 'string') {
    throw new TypeError('Url must be a string. Received ' + strArray[0]);
  }

  // Check before joining a plain protocol so ('http:', '3000') stays explicit.
  const isHostPort = HOST_PORT.test(strArray[0]);

  // If the first part is a plain protocol, we combine it with the next part.
  if (PLAIN_PROTOCOL.test(strArray[0]) && strArray.length > 1) {
    strArray[0] = strArray.shift() + strArray[0];
  }

  // If the first part is a leading slash, we combine it with the next part.
  if (strArray[0] === '/' && strArray.length > 1) {
    strArray[0] = strArray.shift() + strArray[0];
  }

  // There must be two or three slashes in the file protocol, two slashes in anything else.
  if (strArray[0].match(/^file:\/\/\//)) {
    strArray[0] = strArray[0].replace(PROTOCOL_PREFIX, '$1:///');
  } else if (!isHostPort && !strArray[0].match(/^\[.*:.*\]/)) {
    // If the first part is not a host with a port or an IPv6 host, replace the protocol.
    strArray[0] = strArray[0].replace(PROTOCOL_PREFIX, '$1://');
  }

  let prevEndsWithSlash = false;
  let hasSuffix = false;
  let preserveTrailingSlash = false;

  for (let i = 0; i < strArray.length; i++) {
    let component = strArray[i];

    if (typeof component !== 'string') {
      throw new TypeError('Url must be a string. Received ' + component);
    }

    const suffixIndex = component.search(/[?&#]/);
    if (!hasSuffix && suffixIndex !== -1) {
      preserveTrailingSlash = suffixIndex === 0
        ? prevEndsWithSlash
        : component[suffixIndex - 1] === '/';
      hasSuffix = true;
    }

    const startsWithSlash = component.startsWith('/');
    const endsWithSlash = component.endsWith('/');

    if (i > 0) {
      // Removing the starting slashes for each component but the first.
      component = component.replace(/^[\/]+/, '');
    }
    if (i < strArray.length - 1) {
      // Removing the ending slashes for each component but the last.
      component = component.replace(/[\/]+$/, '');
    } else {
      // For the last component we will combine multiple slashes to a single one.
      component = component.replace(/[\/]+$/, '/');
    }

    if (component === '') {
      prevEndsWithSlash = prevEndsWithSlash || startsWithSlash;
      continue;
    }

    resultArray.push(component);
    slashBefore.push(startsWithSlash || prevEndsWithSlash);
    prevEndsWithSlash = endsWithSlash;
  }

  let str = '';

  for (let i = 0; i < resultArray.length; i++) {
    const part = resultArray[i];

    // Do not add a slash if this is the first part.
    if (i === 0) {
      str += part;
      continue;
    }

    const prevPart = resultArray[i - 1]

    // Do not add a slash if the previous part ends with start of the query param or hash.
    if (prevPart && prevPart.endsWith('?')) {
      str += part;
      continue;
    }

    // After a hash, keep the slash only if the input had one (eg: '#', '/tenant' -> '#/tenant').
    if (prevPart.endsWith('#')) {
      str += (slashBefore[i] ? '/' : '') + part;
      continue;
    }

    str += '/' + part;
  }
  // Each input component is now separated by a single slash except the possible first plain protocol part.

  // Keep an explicit path slash, but retain normalization for query-only
  // and hash-only inputs such as '/?a' and '/#a'.
  const suffixIndex = str.search(/[?&#]/);
  str = str.replace(/\/(\?|&|#[^!])/g, (match, separator, offset) =>
    preserveTrailingSlash && offset > 0 && offset + 1 === suffixIndex
      ? match
      : separator
  );

  // replace ? and & in parameters with &
  const hashIndex = str.indexOf('#');
  const beforeHash = hashIndex === -1 ? str : str.slice(0, hashIndex);
  const afterHash = hashIndex === -1 ? '' : str.slice(hashIndex + 1);
  // The base can be empty when the URL starts with a query or hash (eg: '?a=1' or '#a').
  const [base, ...params] = beforeHash.split(/(?:\?|&)+/);
  const query = params.filter(Boolean);
  str = base + (query.length > 0 ? '?': '') + query.join('&') + (afterHash && afterHash.length > 0 ? '#' + afterHash : '');

  return str;
}

export default function urlJoin(...args) {
  const parts = Array.from(Array.isArray(args[0]) ? args[0] : args);
  return normalize(parts);
}