Query String

The querystring module provides utilities for parsing and formatting URL query strings. It can be accessed using:

const querystring = require('querystring');

querystring.escape(str)

• str <string>

The querystring.escape() method performs URL percent-encoding on the given str in a manner that is optimized for the specific requirements of URL query strings.

The querystring.escape() method is used by querystring.stringify() and is generally not expected to be used directly. It is exported primarily to allow application code to provide a replacement percent-encoding implementation if necessary by assigning querystring.escape to an alternative function.

querystring.parse(str[, sep[, eq[, options]]])

• str <string> The URL query string to parse
• sep <string> The substring used to delimit key and value pairs in the query string. Defaults to '&'.
• eq <string>. The substring used to delimit keys and values in the query string. Defaults to '='.
• options <Object>
  • decodeURIComponent <Function> The function to use when decoding percent-encoded characters in the query string. Defaults to querystring.unescape().
  • maxKeys <number> Specifies the maximum number of keys to parse. Defaults to 1000. Specify 0 to remove key counting limitations.

The querystring.parse() method parses a URL query string (str) into a collection of key and value pairs.

For example, the query string 'foo=bar&abc=xyz&abc=123' is parsed into:

{
  foo: 'bar',
  abc: ['xyz', '123']
}

Note: The object returned by the querystring.parse() method does not prototypically inherit from the JavaScript Object. This means that typical Object methods such as obj.toString(), obj.hasOwnProperty(), and others are not defined and will not work.

By default, percent-encoded characters within the query string will be assumed to use UTF-8 encoding. If an alternative character encoding is used, then an alternative decodeURIComponent option will need to be specified as illustrated in the following example:

// Assuming gbkDecodeURIComponent function already exists...

querystring.parse('w=%D6%D0%CE%C4&foo=bar', null, null,
                  { decodeURIComponent: gbkDecodeURIComponent });

querystring.stringify(obj[, sep[, eq[, options]]])

• obj <Object> The object to serialize into a URL query string
• sep <string> The substring used to delimit key and value pairs in the query string. Defaults to '&'.
• eq <string>. The substring used to delimit keys and values in the query string. Defaults to '='.
• options
  • encodeURIComponent <Function> The function to use when converting URL-unsafe characters to percent-encoding in the query string. Defaults to querystring.escape().

The querystring.stringify() method produces a URL query string from a given obj by iterating through the object's "own properties".

It serializes the following types of values passed in obj: <string> | <number> | <boolean> | <string[]> | <number[]> | <boolean[]> Any other input values will be coerced to empty strings.

For example:

querystring.stringify({ foo: 'bar', baz: ['qux', 'quux'], corge: '' });
// returns 'foo=bar&baz=qux&baz=quux&corge='

querystring.stringify({ foo: 'bar', baz: 'qux' }, ';', ':');
// returns 'foo:bar;baz:qux'

By default, characters requiring percent-encoding within the query string will be encoded as UTF-8. If an alternative encoding is required, then an alternative encodeURIComponent option will need to be specified as illustrated in the following example:

// Assuming gbkEncodeURIComponent function already exists,

querystring.stringify({ w: '中文', foo: 'bar' }, null, null,
                      { encodeURIComponent: gbkEncodeURIComponent });

querystring.unescape(str)

• str <string>

The querystring.unescape() method performs decoding of URL percent-encoded characters on the given str.

The querystring.unescape() method is used by querystring.parse() and is generally not expected to be used directly. It is exported primarily to allow application code to provide a replacement decoding implementation if necessary by assigning querystring.unescape to an alternative function.

By default, the querystring.unescape() method will attempt to use the JavaScript built-in decodeURIComponent() method to decode. If that fails, a safer equivalent that does not throw on malformed URLs will be used.