| 
						 | 
						- <p align="center">
 -     <img alt="qs" src="./logos/banner_default.png" width="800" />
 - </p>
 - 
 - # qs <sup>[![Version Badge][npm-version-svg]][package-url]</sup>
 - 
 - [![github actions][actions-image]][actions-url]
 - [![coverage][codecov-image]][codecov-url]
 - [![License][license-image]][license-url]
 - [![Downloads][downloads-image]][downloads-url]
 - [](https://bestpractices.coreinfrastructure.org/projects/9058)
 - 
 - [![npm badge][npm-badge-png]][package-url]
 - 
 - A querystring parsing and stringifying library with some added security.
 - 
 - Lead Maintainer: [Jordan Harband](https://github.com/ljharb)
 - 
 - The **qs** module was originally created and maintained by [TJ Holowaychuk](https://github.com/visionmedia/node-querystring).
 - 
 - ## Usage
 - 
 - ```javascript
 - var qs = require('qs');
 - var assert = require('assert');
 - 
 - var obj = qs.parse('a=c');
 - assert.deepEqual(obj, { a: 'c' });
 - 
 - var str = qs.stringify(obj);
 - assert.equal(str, 'a=c');
 - ```
 - 
 - ### Parsing Objects
 - 
 - [](#preventEval)
 - ```javascript
 - qs.parse(string, [options]);
 - ```
 - 
 - **qs** allows you to create nested objects within your query strings, by surrounding the name of sub-keys with square brackets `[]`.
 - For example, the string `'foo[bar]=baz'` converts to:
 - 
 - ```javascript
 - assert.deepEqual(qs.parse('foo[bar]=baz'), {
 -     foo: {
 -         bar: 'baz'
 -     }
 - });
 - ```
 - 
 - When using the `plainObjects` option the parsed value is returned as a null object, created via `{ __proto__: null }` and as such you should be aware that prototype methods will not exist on it and a user may set those names to whatever value they like:
 - 
 - ```javascript
 - var nullObject = qs.parse('a[hasOwnProperty]=b', { plainObjects: true });
 - assert.deepEqual(nullObject, { a: { hasOwnProperty: 'b' } });
 - ```
 - 
 - By default parameters that would overwrite properties on the object prototype are ignored, if you wish to keep the data from those fields either use `plainObjects` as mentioned above, or set `allowPrototypes` to `true` which will allow user input to overwrite those properties.
 - *WARNING* It is generally a bad idea to enable this option as it can cause problems when attempting to use the properties that have been overwritten.
 - Always be careful with this option.
 - 
 - ```javascript
 - var protoObject = qs.parse('a[hasOwnProperty]=b', { allowPrototypes: true });
 - assert.deepEqual(protoObject, { a: { hasOwnProperty: 'b' } });
 - ```
 - 
 - URI encoded strings work too:
 - 
 - ```javascript
 - assert.deepEqual(qs.parse('a%5Bb%5D=c'), {
 -     a: { b: 'c' }
 - });
 - ```
 - 
 - You can also nest your objects, like `'foo[bar][baz]=foobarbaz'`:
 - 
 - ```javascript
 - assert.deepEqual(qs.parse('foo[bar][baz]=foobarbaz'), {
 -     foo: {
 -         bar: {
 -             baz: 'foobarbaz'
 -         }
 -     }
 - });
 - ```
 - 
 - By default, when nesting objects **qs** will only parse up to 5 children deep.
 - This means if you attempt to parse a string like `'a[b][c][d][e][f][g][h][i]=j'` your resulting object will be:
 - 
 - ```javascript
 - var expected = {
 -     a: {
 -         b: {
 -             c: {
 -                 d: {
 -                     e: {
 -                         f: {
 -                             '[g][h][i]': 'j'
 -                         }
 -                     }
 -                 }
 -             }
 -         }
 -     }
 - };
 - var string = 'a[b][c][d][e][f][g][h][i]=j';
 - assert.deepEqual(qs.parse(string), expected);
 - ```
 - 
 - This depth can be overridden by passing a `depth` option to `qs.parse(string, [options])`:
 - 
 - ```javascript
 - var deep = qs.parse('a[b][c][d][e][f][g][h][i]=j', { depth: 1 });
 - assert.deepEqual(deep, { a: { b: { '[c][d][e][f][g][h][i]': 'j' } } });
 - ```
 - 
 - You can configure **qs** to throw an error when parsing nested input beyond this depth using the `strictDepth` option (defaulted to false):
 - 
 - ```javascript
 - try {
 -     qs.parse('a[b][c][d][e][f][g][h][i]=j', { depth: 1, strictDepth: true });
 - } catch (err) {
 -     assert(err instanceof RangeError);
 -     assert.strictEqual(err.message, 'Input depth exceeded depth option of 1 and strictDepth is true');
 - }
 - ```
 - 
 - The depth limit helps mitigate abuse when **qs** is used to parse user input, and it is recommended to keep it a reasonably small number. The strictDepth option adds a layer of protection by throwing an error when the limit is exceeded, allowing you to catch and handle such cases.
 - 
 - For similar reasons, by default **qs** will only parse up to 1000 parameters. This can be overridden by passing a `parameterLimit` option:
 - 
 - ```javascript
 - var limited = qs.parse('a=b&c=d', { parameterLimit: 1 });
 - assert.deepEqual(limited, { a: 'b' });
 - ```
 - 
 - If you want an error to be thrown whenever the a limit is exceeded (eg, `parameterLimit`, `arrayLimit`), set the `throwOnLimitExceeded` option to `true`. This option will generate a descriptive error if the query string exceeds a configured limit.
 - ```javascript
 - try {
 -     qs.parse('a=1&b=2&c=3&d=4', { parameterLimit: 3, throwOnLimitExceeded: true });
 - } catch (err) {
 -     assert(err instanceof Error);
 -     assert.strictEqual(err.message, 'Parameter limit exceeded. Only 3 parameters allowed.');
 - }
 - ```
 - 
 - When `throwOnLimitExceeded` is set to `false` (default), **qs** will parse up to the specified `parameterLimit` and ignore the rest without throwing an error.
 - 
 - To bypass the leading question mark, use `ignoreQueryPrefix`:
 - 
 - ```javascript
 - var prefixed = qs.parse('?a=b&c=d', { ignoreQueryPrefix: true });
 - assert.deepEqual(prefixed, { a: 'b', c: 'd' });
 - ```
 - 
 - An optional delimiter can also be passed:
 - 
 - ```javascript
 - var delimited = qs.parse('a=b;c=d', { delimiter: ';' });
 - assert.deepEqual(delimited, { a: 'b', c: 'd' });
 - ```
 - 
 - Delimiters can be a regular expression too:
 - 
 - ```javascript
 - var regexed = qs.parse('a=b;c=d,e=f', { delimiter: /[;,]/ });
 - assert.deepEqual(regexed, { a: 'b', c: 'd', e: 'f' });
 - ```
 - 
 - Option `allowDots` can be used to enable dot notation:
 - 
 - ```javascript
 - var withDots = qs.parse('a.b=c', { allowDots: true });
 - assert.deepEqual(withDots, { a: { b: 'c' } });
 - ```
 - 
 - Option `decodeDotInKeys` can be used to decode dots in keys
 - Note: it implies `allowDots`, so `parse` will error if you set `decodeDotInKeys` to `true`, and `allowDots` to `false`.
 - 
 - ```javascript
 - var withDots = qs.parse('name%252Eobj.first=John&name%252Eobj.last=Doe', { decodeDotInKeys: true });
 - assert.deepEqual(withDots, { 'name.obj': { first: 'John', last: 'Doe' }});
 - ```
 - 
 - Option `allowEmptyArrays` can be used to allowing empty array values in object
 - ```javascript
 - var withEmptyArrays = qs.parse('foo[]&bar=baz', { allowEmptyArrays: true });
 - assert.deepEqual(withEmptyArrays, { foo: [], bar: 'baz' });
 - ```
 - 
 - Option `duplicates` can be used to change the behavior when duplicate keys are encountered
 - ```javascript
 - assert.deepEqual(qs.parse('foo=bar&foo=baz'), { foo: ['bar', 'baz'] });
 - assert.deepEqual(qs.parse('foo=bar&foo=baz', { duplicates: 'combine' }), { foo: ['bar', 'baz'] });
 - assert.deepEqual(qs.parse('foo=bar&foo=baz', { duplicates: 'first' }), { foo: 'bar' });
 - assert.deepEqual(qs.parse('foo=bar&foo=baz', { duplicates: 'last' }), { foo: 'baz' });
 - ```
 - 
 - If you have to deal with legacy browsers or services, there's also support for decoding percent-encoded octets as iso-8859-1:
 - 
 - ```javascript
 - var oldCharset = qs.parse('a=%A7', { charset: 'iso-8859-1' });
 - assert.deepEqual(oldCharset, { a: '§' });
 - ```
 - 
 - Some services add an initial `utf8=✓` value to forms so that old Internet Explorer versions are more likely to submit the form as utf-8.
 - Additionally, the server can check the value against wrong encodings of the checkmark character and detect that a query string or `application/x-www-form-urlencoded` body was *not* sent as utf-8, eg. if the form had an `accept-charset` parameter or the containing page had a different character set.
 - 
 - **qs** supports this mechanism via the `charsetSentinel` option.
 - If specified, the `utf8` parameter will be omitted from the returned object.
 - It will be used to switch to `iso-8859-1`/`utf-8` mode depending on how the checkmark is encoded.
 - 
 - **Important**: When you specify both the `charset` option and the `charsetSentinel` option, the `charset` will be overridden when the request contains a `utf8` parameter from which the actual charset can be deduced.
 - In that sense the `charset` will behave as the default charset rather than the authoritative charset.
 - 
 - ```javascript
 - var detectedAsUtf8 = qs.parse('utf8=%E2%9C%93&a=%C3%B8', {
 -     charset: 'iso-8859-1',
 -     charsetSentinel: true
 - });
 - assert.deepEqual(detectedAsUtf8, { a: 'ø' });
 - 
 - // Browsers encode the checkmark as ✓ when submitting as iso-8859-1:
 - var detectedAsIso8859_1 = qs.parse('utf8=%26%2310003%3B&a=%F8', {
 -     charset: 'utf-8',
 -     charsetSentinel: true
 - });
 - assert.deepEqual(detectedAsIso8859_1, { a: 'ø' });
 - ```
 - 
 - If you want to decode the `&#...;` syntax to the actual character, you can specify the `interpretNumericEntities` option as well:
 - 
 - ```javascript
 - var detectedAsIso8859_1 = qs.parse('a=%26%239786%3B', {
 -     charset: 'iso-8859-1',
 -     interpretNumericEntities: true
 - });
 - assert.deepEqual(detectedAsIso8859_1, { a: '☺' });
 - ```
 - 
 - It also works when the charset has been detected in `charsetSentinel` mode.
 - 
 - ### Parsing Arrays
 - 
 - **qs** can also parse arrays using a similar `[]` notation:
 - 
 - ```javascript
 - var withArray = qs.parse('a[]=b&a[]=c');
 - assert.deepEqual(withArray, { a: ['b', 'c'] });
 - ```
 - 
 - You may specify an index as well:
 - 
 - ```javascript
 - var withIndexes = qs.parse('a[1]=c&a[0]=b');
 - assert.deepEqual(withIndexes, { a: ['b', 'c'] });
 - ```
 - 
 - Note that the only difference between an index in an array and a key in an object is that the value between the brackets must be a number to create an array.
 - When creating arrays with specific indices, **qs** will compact a sparse array to only the existing values preserving their order:
 - 
 - ```javascript
 - var noSparse = qs.parse('a[1]=b&a[15]=c');
 - assert.deepEqual(noSparse, { a: ['b', 'c'] });
 - ```
 - 
 - You may also use `allowSparse` option to parse sparse arrays:
 - 
 - ```javascript
 - var sparseArray = qs.parse('a[1]=2&a[3]=5', { allowSparse: true });
 - assert.deepEqual(sparseArray, { a: [, '2', , '5'] });
 - ```
 - 
 - Note that an empty string is also a value, and will be preserved:
 - 
 - ```javascript
 - var withEmptyString = qs.parse('a[]=&a[]=b');
 - assert.deepEqual(withEmptyString, { a: ['', 'b'] });
 - 
 - var withIndexedEmptyString = qs.parse('a[0]=b&a[1]=&a[2]=c');
 - assert.deepEqual(withIndexedEmptyString, { a: ['b', '', 'c'] });
 - ```
 - 
 - **qs** will also limit specifying indices in an array to a maximum index of `20`.
 - Any array members with an index of greater than `20` will instead be converted to an object with the index as the key.
 - This is needed to handle cases when someone sent, for example, `a[999999999]` and it will take significant time to iterate over this huge array.
 - 
 - ```javascript
 - var withMaxIndex = qs.parse('a[100]=b');
 - assert.deepEqual(withMaxIndex, { a: { '100': 'b' } });
 - ```
 - 
 - This limit can be overridden by passing an `arrayLimit` option:
 - 
 - ```javascript
 - var withArrayLimit = qs.parse('a[1]=b', { arrayLimit: 0 });
 - assert.deepEqual(withArrayLimit, { a: { '1': 'b' } });
 - ```
 - 
 - If you want to throw an error whenever the array limit is exceeded, set the `throwOnLimitExceeded` option to `true`. This option will generate a descriptive error if the query string exceeds a configured limit.
 - ```javascript
 - try {
 -     qs.parse('a[1]=b', { arrayLimit: 0, throwOnLimitExceeded: true });
 - } catch (err) {
 -     assert(err instanceof Error);
 -     assert.strictEqual(err.message, 'Array limit exceeded. Only 0 elements allowed in an array.');
 - }
 - ```
 - 
 - When `throwOnLimitExceeded` is set to `false` (default), **qs** will parse up to the specified `arrayLimit` and if the limit is exceeded, the array will instead be converted to an object with the index as the key
 - 
 - To disable array parsing entirely, set `parseArrays` to `false`.
 - 
 - ```javascript
 - var noParsingArrays = qs.parse('a[]=b', { parseArrays: false });
 - assert.deepEqual(noParsingArrays, { a: { '0': 'b' } });
 - ```
 - 
 - If you mix notations, **qs** will merge the two items into an object:
 - 
 - ```javascript
 - var mixedNotation = qs.parse('a[0]=b&a[b]=c');
 - assert.deepEqual(mixedNotation, { a: { '0': 'b', b: 'c' } });
 - ```
 - 
 - You can also create arrays of objects:
 - 
 - ```javascript
 - var arraysOfObjects = qs.parse('a[][b]=c');
 - assert.deepEqual(arraysOfObjects, { a: [{ b: 'c' }] });
 - ```
 - 
 - Some people use comma to join array, **qs** can parse it:
 - ```javascript
 - var arraysOfObjects = qs.parse('a=b,c', { comma: true })
 - assert.deepEqual(arraysOfObjects, { a: ['b', 'c'] })
 - ```
 - (_this cannot convert nested objects, such as `a={b:1},{c:d}`_)
 - 
 - ### Parsing primitive/scalar values (numbers, booleans, null, etc)
 - 
 - By default, all values are parsed as strings.
 - This behavior will not change and is explained in [issue #91](https://github.com/ljharb/qs/issues/91).
 - 
 - ```javascript
 - var primitiveValues = qs.parse('a=15&b=true&c=null');
 - assert.deepEqual(primitiveValues, { a: '15', b: 'true', c: 'null' });
 - ```
 - 
 - If you wish to auto-convert values which look like numbers, booleans, and other values into their primitive counterparts, you can use the [query-types Express JS middleware](https://github.com/xpepermint/query-types) which will auto-convert all request query parameters.
 - 
 - ### Stringifying
 - 
 - [](#preventEval)
 - ```javascript
 - qs.stringify(object, [options]);
 - ```
 - 
 - When stringifying, **qs** by default URI encodes output. Objects are stringified as you would expect:
 - 
 - ```javascript
 - assert.equal(qs.stringify({ a: 'b' }), 'a=b');
 - assert.equal(qs.stringify({ a: { b: 'c' } }), 'a%5Bb%5D=c');
 - ```
 - 
 - This encoding can be disabled by setting the `encode` option to `false`:
 - 
 - ```javascript
 - var unencoded = qs.stringify({ a: { b: 'c' } }, { encode: false });
 - assert.equal(unencoded, 'a[b]=c');
 - ```
 - 
 - Encoding can be disabled for keys by setting the `encodeValuesOnly` option to `true`:
 - ```javascript
 - var encodedValues = qs.stringify(
 -     { a: 'b', c: ['d', 'e=f'], f: [['g'], ['h']] },
 -     { encodeValuesOnly: true }
 - );
 - assert.equal(encodedValues,'a=b&c[0]=d&c[1]=e%3Df&f[0][0]=g&f[1][0]=h');
 - ```
 - 
 - This encoding can also be replaced by a custom encoding method set as `encoder` option:
 - 
 - ```javascript
 - var encoded = qs.stringify({ a: { b: 'c' } }, { encoder: function (str) {
 -     // Passed in values `a`, `b`, `c`
 -     return // Return encoded string
 - }})
 - ```
 - 
 - _(Note: the `encoder` option does not apply if `encode` is `false`)_
 - 
 - Analogue to the `encoder` there is a `decoder` option for `parse` to override decoding of properties and values:
 - 
 - ```javascript
 - var decoded = qs.parse('x=z', { decoder: function (str) {
 -     // Passed in values `x`, `z`
 -     return // Return decoded string
 - }})
 - ```
 - 
 - You can encode keys and values using different logic by using the type argument provided to the encoder:
 - 
 - ```javascript
 - var encoded = qs.stringify({ a: { b: 'c' } }, { encoder: function (str, defaultEncoder, charset, type) {
 -     if (type === 'key') {
 -         return // Encoded key
 -     } else if (type === 'value') {
 -         return // Encoded value
 -     }
 - }})
 - ```
 - 
 - The type argument is also provided to the decoder:
 - 
 - ```javascript
 - var decoded = qs.parse('x=z', { decoder: function (str, defaultDecoder, charset, type) {
 -     if (type === 'key') {
 -         return // Decoded key
 -     } else if (type === 'value') {
 -         return // Decoded value
 -     }
 - }})
 - ```
 - 
 - Examples beyond this point will be shown as though the output is not URI encoded for clarity.
 - Please note that the return values in these cases *will* be URI encoded during real usage.
 - 
 - When arrays are stringified, they follow the `arrayFormat` option, which defaults to `indices`:
 - 
 - ```javascript
 - qs.stringify({ a: ['b', 'c', 'd'] });
 - // 'a[0]=b&a[1]=c&a[2]=d'
 - ```
 - 
 - You may override this by setting the `indices` option to `false`, or to be more explicit, the `arrayFormat` option to `repeat`:
 - 
 - ```javascript
 - qs.stringify({ a: ['b', 'c', 'd'] }, { indices: false });
 - // 'a=b&a=c&a=d'
 - ```
 - 
 - You may use the `arrayFormat` option to specify the format of the output array:
 - 
 - ```javascript
 - qs.stringify({ a: ['b', 'c'] }, { arrayFormat: 'indices' })
 - // 'a[0]=b&a[1]=c'
 - qs.stringify({ a: ['b', 'c'] }, { arrayFormat: 'brackets' })
 - // 'a[]=b&a[]=c'
 - qs.stringify({ a: ['b', 'c'] }, { arrayFormat: 'repeat' })
 - // 'a=b&a=c'
 - qs.stringify({ a: ['b', 'c'] }, { arrayFormat: 'comma' })
 - // 'a=b,c'
 - ```
 - 
 - Note: when using `arrayFormat` set to `'comma'`, you can also pass the `commaRoundTrip` option set to `true` or `false`, to append `[]` on single-item arrays, so that they can round trip through a parse.
 - 
 - When objects are stringified, by default they use bracket notation:
 - 
 - ```javascript
 - qs.stringify({ a: { b: { c: 'd', e: 'f' } } });
 - // 'a[b][c]=d&a[b][e]=f'
 - ```
 - 
 - You may override this to use dot notation by setting the `allowDots` option to `true`:
 - 
 - ```javascript
 - qs.stringify({ a: { b: { c: 'd', e: 'f' } } }, { allowDots: true });
 - // 'a.b.c=d&a.b.e=f'
 - ```
 - 
 - You may encode the dot notation in the keys of object with option `encodeDotInKeys` by setting it to `true`:
 - Note: it implies `allowDots`, so `stringify` will error if you set `decodeDotInKeys` to `true`, and `allowDots` to `false`.
 - Caveat: when `encodeValuesOnly` is `true` as well as `encodeDotInKeys`, only dots in keys and nothing else will be encoded.
 - ```javascript
 - qs.stringify({ "name.obj": { "first": "John", "last": "Doe" } }, { allowDots: true, encodeDotInKeys: true })
 - // 'name%252Eobj.first=John&name%252Eobj.last=Doe'
 - ```
 - 
 - You may allow empty array values by setting the `allowEmptyArrays` option to `true`:
 - ```javascript
 - qs.stringify({ foo: [], bar: 'baz' }, { allowEmptyArrays: true });
 - // 'foo[]&bar=baz'
 - ```
 - 
 - Empty strings and null values will omit the value, but the equals sign (=) remains in place:
 - 
 - ```javascript
 - assert.equal(qs.stringify({ a: '' }), 'a=');
 - ```
 - 
 - Key with no values (such as an empty object or array) will return nothing:
 - 
 - ```javascript
 - assert.equal(qs.stringify({ a: [] }), '');
 - assert.equal(qs.stringify({ a: {} }), '');
 - assert.equal(qs.stringify({ a: [{}] }), '');
 - assert.equal(qs.stringify({ a: { b: []} }), '');
 - assert.equal(qs.stringify({ a: { b: {}} }), '');
 - ```
 - 
 - Properties that are set to `undefined` will be omitted entirely:
 - 
 - ```javascript
 - assert.equal(qs.stringify({ a: null, b: undefined }), 'a=');
 - ```
 - 
 - The query string may optionally be prepended with a question mark:
 - 
 - ```javascript
 - assert.equal(qs.stringify({ a: 'b', c: 'd' }, { addQueryPrefix: true }), '?a=b&c=d');
 - ```
 - 
 - The delimiter may be overridden with stringify as well:
 - 
 - ```javascript
 - assert.equal(qs.stringify({ a: 'b', c: 'd' }, { delimiter: ';' }), 'a=b;c=d');
 - ```
 - 
 - If you only want to override the serialization of `Date` objects, you can provide a `serializeDate` option:
 - 
 - ```javascript
 - var date = new Date(7);
 - assert.equal(qs.stringify({ a: date }), 'a=1970-01-01T00:00:00.007Z'.replace(/:/g, '%3A'));
 - assert.equal(
 -     qs.stringify({ a: date }, { serializeDate: function (d) { return d.getTime(); } }),
 -     'a=7'
 - );
 - ```
 - 
 - You may use the `sort` option to affect the order of parameter keys:
 - 
 - ```javascript
 - function alphabeticalSort(a, b) {
 -     return a.localeCompare(b);
 - }
 - assert.equal(qs.stringify({ a: 'c', z: 'y', b : 'f' }, { sort: alphabeticalSort }), 'a=c&b=f&z=y');
 - ```
 - 
 - Finally, you can use the `filter` option to restrict which keys will be included in the stringified output.
 - If you pass a function, it will be called for each key to obtain the replacement value.
 - Otherwise, if you pass an array, it will be used to select properties and array indices for stringification:
 - 
 - ```javascript
 - function filterFunc(prefix, value) {
 -     if (prefix == 'b') {
 -         // Return an `undefined` value to omit a property.
 -         return;
 -     }
 -     if (prefix == 'e[f]') {
 -         return value.getTime();
 -     }
 -     if (prefix == 'e[g][0]') {
 -         return value * 2;
 -     }
 -     return value;
 - }
 - qs.stringify({ a: 'b', c: 'd', e: { f: new Date(123), g: [2] } }, { filter: filterFunc });
 - // 'a=b&c=d&e[f]=123&e[g][0]=4'
 - qs.stringify({ a: 'b', c: 'd', e: 'f' }, { filter: ['a', 'e'] });
 - // 'a=b&e=f'
 - qs.stringify({ a: ['b', 'c', 'd'], e: 'f' }, { filter: ['a', 0, 2] });
 - // 'a[0]=b&a[2]=d'
 - ```
 - 
 - You could also use `filter` to inject custom serialization for user defined types.
 - Consider you're working with some api that expects query strings of the format for ranges:
 - 
 - ```
 - https://domain.com/endpoint?range=30...70
 - ```
 - 
 - For which you model as:
 - 
 - ```javascript
 - class Range {
 -     constructor(from, to) {
 -         this.from = from;
 -         this.to = to;
 -     }
 - }
 - ```
 - 
 - You could _inject_ a custom serializer to handle values of this type:
 - 
 - ```javascript
 - qs.stringify(
 -     {
 -         range: new Range(30, 70),
 -     },
 -     {
 -         filter: (prefix, value) => {
 -             if (value instanceof Range) {
 -                 return `${value.from}...${value.to}`;
 -             }
 -             // serialize the usual way
 -             return value;
 -         },
 -     }
 - );
 - // range=30...70
 - ```
 - 
 - ### Handling of `null` values
 - 
 - By default, `null` values are treated like empty strings:
 - 
 - ```javascript
 - var withNull = qs.stringify({ a: null, b: '' });
 - assert.equal(withNull, 'a=&b=');
 - ```
 - 
 - Parsing does not distinguish between parameters with and without equal signs.
 - Both are converted to empty strings.
 - 
 - ```javascript
 - var equalsInsensitive = qs.parse('a&b=');
 - assert.deepEqual(equalsInsensitive, { a: '', b: '' });
 - ```
 - 
 - To distinguish between `null` values and empty strings use the `strictNullHandling` flag. In the result string the `null`
 - values have no `=` sign:
 - 
 - ```javascript
 - var strictNull = qs.stringify({ a: null, b: '' }, { strictNullHandling: true });
 - assert.equal(strictNull, 'a&b=');
 - ```
 - 
 - To parse values without `=` back to `null` use the `strictNullHandling` flag:
 - 
 - ```javascript
 - var parsedStrictNull = qs.parse('a&b=', { strictNullHandling: true });
 - assert.deepEqual(parsedStrictNull, { a: null, b: '' });
 - ```
 - 
 - To completely skip rendering keys with `null` values, use the `skipNulls` flag:
 - 
 - ```javascript
 - var nullsSkipped = qs.stringify({ a: 'b', c: null}, { skipNulls: true });
 - assert.equal(nullsSkipped, 'a=b');
 - ```
 - 
 - If you're communicating with legacy systems, you can switch to `iso-8859-1` using the `charset` option:
 - 
 - ```javascript
 - var iso = qs.stringify({ æ: 'æ' }, { charset: 'iso-8859-1' });
 - assert.equal(iso, '%E6=%E6');
 - ```
 - 
 - Characters that don't exist in `iso-8859-1` will be converted to numeric entities, similar to what browsers do:
 - 
 - ```javascript
 - var numeric = qs.stringify({ a: '☺' }, { charset: 'iso-8859-1' });
 - assert.equal(numeric, 'a=%26%239786%3B');
 - ```
 - 
 - You can use the `charsetSentinel` option to announce the character by including an `utf8=✓` parameter with the proper encoding if the checkmark, similar to what Ruby on Rails and others do when submitting forms.
 - 
 - ```javascript
 - var sentinel = qs.stringify({ a: '☺' }, { charsetSentinel: true });
 - assert.equal(sentinel, 'utf8=%E2%9C%93&a=%E2%98%BA');
 - 
 - var isoSentinel = qs.stringify({ a: 'æ' }, { charsetSentinel: true, charset: 'iso-8859-1' });
 - assert.equal(isoSentinel, 'utf8=%26%2310003%3B&a=%E6');
 - ```
 - 
 - ### Dealing with special character sets
 - 
 - By default the encoding and decoding of characters is done in `utf-8`, and `iso-8859-1` support is also built in via the `charset` parameter.
 - 
 - If you wish to encode querystrings to a different character set (i.e.
 - [Shift JIS](https://en.wikipedia.org/wiki/Shift_JIS)) you can use the
 - [`qs-iconv`](https://github.com/martinheidegger/qs-iconv) library:
 - 
 - ```javascript
 - var encoder = require('qs-iconv/encoder')('shift_jis');
 - var shiftJISEncoded = qs.stringify({ a: 'こんにちは!' }, { encoder: encoder });
 - assert.equal(shiftJISEncoded, 'a=%82%B1%82%F1%82%C9%82%BF%82%CD%81I');
 - ```
 - 
 - This also works for decoding of query strings:
 - 
 - ```javascript
 - var decoder = require('qs-iconv/decoder')('shift_jis');
 - var obj = qs.parse('a=%82%B1%82%F1%82%C9%82%BF%82%CD%81I', { decoder: decoder });
 - assert.deepEqual(obj, { a: 'こんにちは!' });
 - ```
 - 
 - ### RFC 3986 and RFC 1738 space encoding
 - 
 - RFC3986 used as default option and encodes ' ' to *%20* which is backward compatible.
 - In the same time, output can be stringified as per RFC1738 with ' ' equal to '+'.
 - 
 - ```
 - assert.equal(qs.stringify({ a: 'b c' }), 'a=b%20c');
 - assert.equal(qs.stringify({ a: 'b c' }, { format : 'RFC3986' }), 'a=b%20c');
 - assert.equal(qs.stringify({ a: 'b c' }, { format : 'RFC1738' }), 'a=b+c');
 - ```
 - 
 - ## Security
 - 
 - Please email [@ljharb](https://github.com/ljharb) or see https://tidelift.com/security if you have a potential security vulnerability to report.
 - 
 - ## qs for enterprise
 - 
 - Available as part of the Tidelift Subscription
 - 
 - The maintainers of qs and thousands of other packages are working with Tidelift to deliver commercial support and maintenance for the open source dependencies you use to build your applications.
 - Save time, reduce risk, and improve code health, while paying the maintainers of the exact dependencies you use.
 - [Learn more.](https://tidelift.com/subscription/pkg/npm-qs?utm_source=npm-qs&utm_medium=referral&utm_campaign=enterprise&utm_term=repo)
 - 
 - [package-url]: https://npmjs.org/package/qs
 - [npm-version-svg]: https://versionbadg.es/ljharb/qs.svg
 - [deps-svg]: https://david-dm.org/ljharb/qs.svg
 - [deps-url]: https://david-dm.org/ljharb/qs
 - [dev-deps-svg]: https://david-dm.org/ljharb/qs/dev-status.svg
 - [dev-deps-url]: https://david-dm.org/ljharb/qs#info=devDependencies
 - [npm-badge-png]: https://nodei.co/npm/qs.png?downloads=true&stars=true
 - [license-image]: https://img.shields.io/npm/l/qs.svg
 - [license-url]: LICENSE
 - [downloads-image]: https://img.shields.io/npm/dm/qs.svg
 - [downloads-url]: https://npm-stat.com/charts.html?package=qs
 - [codecov-image]: https://codecov.io/gh/ljharb/qs/branch/main/graphs/badge.svg
 - [codecov-url]: https://app.codecov.io/gh/ljharb/qs/
 - [actions-image]: https://img.shields.io/endpoint?url=https://github-actions-badge-u3jn4tfpocch.runkit.sh/ljharb/qs
 - [actions-url]: https://github.com/ljharb/qs/actions
 - 
 - ## Acknowledgements
 - 
 - qs logo by [NUMI](https://github.com/numi-hq/open-design):
 - 
 - [<img src="https://raw.githubusercontent.com/numi-hq/open-design/main/assets/numi-lockup.png" alt="NUMI Logo" style="width: 200px;"/>](https://numi.tech/?ref=qs)
 
 
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