Function parseParams

lib/internal/url.js:1259–1354

(qs)

// application/x-www-form-urlencoded parser
// Ref: https://url.spec.whatwg.org/#concept-urlencoded-parser
function parseParams(qs) {
  const out = [];
  let seenSep = false;
  let buf = '';
  let encoded = false;
  let encodeCheck = 0;
  let i = qs[0] === '?' ? 1 : 0;
  let pairStart = i;
  let lastPos = i;
  for (; i < qs.length; ++i) {
    const code = StringPrototypeCharCodeAt(qs, i);

    // Try matching key/value pair separator
    if (code === CHAR_AMPERSAND) {
      if (pairStart === i) {
        // We saw an empty substring between pair separators
        lastPos = pairStart = i + 1;
        continue;
      }

      if (lastPos < i)
        buf += qs.slice(lastPos, i);
      if (encoded)
        buf = querystring.unescape(buf);
      out.push(buf);

      // If `buf` is the key, add an empty value.
      if (!seenSep)
        out.push('');

      seenSep = false;
      buf = '';
      encoded = false;
      encodeCheck = 0;
      lastPos = pairStart = i + 1;
      continue;
    }

    // Try matching key/value separator (e.g. '=') if we haven't already
    if (!seenSep && code === CHAR_EQUAL) {
      // Key/value separator match!
      if (lastPos < i)
        buf += qs.slice(lastPos, i);
      if (encoded)
        buf = querystring.unescape(buf);
      out.push(buf);

      seenSep = true;
      buf = '';
      encoded = false;
      encodeCheck = 0;
      lastPos = i + 1;
      continue;
    }

    // Handle + and percent decoding.
    if (code === CHAR_PLUS) {
      if (lastPos < i)