node/lib/querystring.js

// Query String Utilities

var QueryString = exports;
var urlDecode = process.binding("http_parser").urlDecode;

// a safe fast alternative to decodeURIComponent
QueryString.unescape = urlDecode;

QueryString.escape = function (str) {
  return encodeURIComponent(str);
};

var stringifyPrimitive = function(v) {
  switch (typeof v) {
    case "string":
      return v;

    case "boolean":
      return v ? "true" : "false";

    case "number":
      return isFinite(v) ? v : "";

    default:
      return "";
  }
};

/**
 * <p>Converts an arbitrary value to a Query String representation.</p>
 *
 * <p>Objects with cyclical references will trigger an exception.</p>
 *
 * @method stringify
 * @param obj {Variant} any arbitrary value to convert to query string
 * @param sep {String} (optional) Character that should join param k=v pairs together. Default: "&"
 * @param eq  {String} (optional) Character that should join keys to their values. Default: "="
 * @param name {String} (optional) Name of the current key, for handling children recursively.
 * @static
 */
QueryString.stringify = QueryString.encode = function (obj, sep, eq, name) {
  sep = sep || "&";
  eq = eq || "=";
  obj = (obj === null) ? undefined : obj;

  switch (typeof obj) {
    case "object":
      return Object.keys(obj).map(function(k) {
        if (Array.isArray(obj[k])) {
          return obj[k].map(function(v) {
            return QueryString.escape(stringifyPrimitive(k)) +
                   eq +
                   QueryString.escape(stringifyPrimitive(v));
          }).join(sep);
        } else {
          return QueryString.escape(stringifyPrimitive(k)) + 
                 eq +
                 QueryString.escape(stringifyPrimitive(obj[k]));
        }
      }).join(sep);

    default:
      return (name) ?
        QueryString.escape(stringifyPrimitive(name)) + eq +
          QueryString.escape(stringifyPrimitive(obj)) :
        "";
  }
};

// Parse a key=val string.
QueryString.parse = QueryString.decode = function (qs, sep, eq) {
  sep = sep || "&";
  eq = eq || "=";
  var obj = {};

  if (typeof qs !== 'string') {
    return obj;
  }

  qs.split(sep).forEach(function(kvp) {
    var x = kvp.split(eq);
    var k = QueryString.unescape(x[0], true);
    var v = QueryString.unescape(x.slice(1).join(eq), true);

    if (!(k in obj)) {
        obj[k] = v;
    } else if (!Array.isArray(obj[k])) {
        obj[k] = [obj[k], v];
    } else {
        obj[k].push(v);
    }
  });

  return obj;
};