Fix custom type functions with array formats

Fixes #401

Author: sindresorhus

base.d.ts

@@ -182,14 +182,14 @@ export type ParseOptions = {
 
 	Use this option to explicitly define the type of a specific parameter—particularly useful in cases where the type might otherwise be ambiguous (e.g., phone numbers or IDs).
 
-	You can also provide a custom function to transform the value. The function will receive the raw string and should return the desired parsed result (see Example 4).
+	You can also provide a custom function to transform the value. The function will receive the raw string and should return the desired parsed result. When used with array formats (like `comma`, `separator`, `bracket`, etc.), the function is applied to each array element individually.
 
 	NOTE: Array types (`string[]`, `number[]`) are ignored if `arrayFormat` is set to `'none'`.
 
 	@default {}
 
 	@example
-	Parse `phoneNumber` as a string, overriding the `parseNumber` option:
+	Parse `phoneNumber` as a string, overriding the `parseNumbers` option:
 	```
 	import queryString from 'query-string';
 
@@ -203,12 +203,12 @@ export type ParseOptions = {
 	```
 
 	@example
-	Parse `items` as an array of strings, overriding the `parseNumber` option:
+	Parse `items` as an array of strings, overriding the `parseNumbers` option:
 	```
 	import queryString from 'query-string';
 
 	queryString.parse('?age=20&items=1%2C2%2C3', {
-		parseNumber: true,
+		parseNumbers: true,
 		types: {
 			items: 'string[]',
 		}
@@ -236,12 +236,27 @@ export type ParseOptions = {
 
 	queryString.parse('?age=20&id=01234&zipcode=90210', {
 		types: {
-			age: (value) => value * 2,
+			age: value => value * 2,
 		}
 	});
 	//=> {age: 40, id: '01234', zipcode: '90210'}
 	```
 
+	@example
+	Custom functions are applied to each array element when using array formats:
+	```
+	import queryString from 'query-string';
+
+	// With arrays, the function is applied to each element
+	queryString.parse('?scores=10,20,30', {
+		arrayFormat: 'comma',
+		types: {
+			scores: value => Number(value) * 2,
+		}
+	});
+	//=> {scores: [20, 40, 60]}
+	```
+
 	@example
 	Array types are ignored when `arrayFormat` is set to `'none'`:
 	```
@@ -267,7 +282,7 @@ export type ParseOptions = {
 			items: 'string[]',
 			price: 'string',
 			numbers: 'number[]',
-			double: (value) => value * 2,
+			double: value => value * 2,
 			number: 'number',
 		},
 	});

base.js

@@ -403,7 +403,8 @@ export function parse(query, options) {
 	for (const [key, value] of Object.entries(returnValue)) {
 		if (typeof value === 'object' && value !== null && options.types[key] !== 'string') {
 			for (const [key2, value2] of Object.entries(value)) {
-				const type = options.types[key] ? options.types[key].replace('[]', '') : undefined;
+				const typeOption = options.types[key];
+				const type = typeof typeOption === 'function' ? typeOption : (typeOption ? typeOption.replace('[]', '') : undefined);
 				value[key2] = parseValue(value2, options, type);
 			}
 		} else if (typeof value === 'object' && value !== null && options.types[key] === 'string') {

readme.md

@@ -201,13 +201,11 @@ Parse the value as a boolean type instead of string type if it's a boolean.
 Type: `object`\
 Default: `{}`
 
-
 Specifies a schema for parsing query values with explicit type declarations. When defined, the types provided here take precedence over general parsing options such as `parseNumbers`, `parseBooleans`, and `arrayFormat`.
 
 Use this option to explicitly define the type of a specific parameter—particularly useful in cases where the type might otherwise be ambiguous (e.g., phone numbers or IDs).
 
-You can also provide a custom function to transform the value. The function will receive the raw string and should return the desired parsed result.
-
+You can also provide a custom function to transform the value. The function will receive the raw string and should return the desired parsed result. When used with array formats (like `comma`, `separator`, `bracket`, etc.), the function is applied to each array element individually.
 
 Supported Types:
 
@@ -281,17 +279,26 @@ queryString.parse('?age=20&items=1%2C2%2C3', {
 //=> {age: '20', items: [1, 2, 3]}
 ```
 
-- `'Function'`: Provide a custom function as the parameter type. The parameter's value will equal the function's return value.
+- `'Function'`: Provide a custom function as the parameter type. The parameter's value will equal the function's return value. When used with array formats (like `comma`, `separator`, `bracket`, etc.), the function is applied to each array element individually.
 
 ```js
 import queryString from 'query-string';
 
 queryString.parse('?age=20&id=01234&zipcode=90210', {
 	types: {
-		age: (value) => value * 2,
+		age: value => value * 2,
 	}
 });
 //=> {age: 40, id: '01234', zipcode: '90210'}
+
+// With arrays, the function is applied to each element
+queryString.parse('?scores=10,20,30', {
+	arrayFormat: 'comma',
+	types: {
+		scores: value => Number(value) * 2,
+	}
+});
+//=> {scores: [20, 40, 60]}
 ```
 
 NOTE: Array types (`string[]`, `number[]`) are ignored if `arrayFormat` is set to `'none'`.
@@ -314,7 +321,7 @@ import queryString from 'query-string';
 
 queryString.parse('?age=20&id=01234&zipcode=90210', {
 	types: {
-		age: (value) => value * 2,
+		age: value => value * 2,
 	}
 });
 //=> {age: 40, id: '01234', zipcode: '90210'}

test/parse.js

@@ -625,3 +625,57 @@ test('types option: boolean type accepts an empty string as true', t => {
 		},
 	);
 });
+
+test('types option: function types with arrays apply to each element', t => {
+	// Test with comma format
+	t.deepEqual(queryString.parse('scores=10,20,30', {
+		arrayFormat: 'comma',
+		types: {
+			scores: value => Number(value) * 2,
+		},
+	}), {
+		scores: [20, 40, 60],
+	});
+
+	// Test with bracket format
+	t.deepEqual(queryString.parse('scores[]=5&scores[]=10&scores[]=15', {
+		arrayFormat: 'bracket',
+		types: {
+			scores: value => Number(value) + 10,
+		},
+	}), {
+		scores: [15, 20, 25],
+	});
+
+	// Test with separator format
+	t.deepEqual(queryString.parse('scores=1|2|3', {
+		arrayFormat: 'separator',
+		arrayFormatSeparator: '|',
+		types: {
+			scores: value => `item-${value}`,
+		},
+	}), {
+		scores: ['item-1', 'item-2', 'item-3'],
+	});
+
+	// Test function with single value still works
+	t.deepEqual(queryString.parse('score=42', {
+		types: {
+			score: value => Number(value) / 2,
+		},
+	}), {
+		score: 21,
+	});
+
+	// Test mixed types in same query
+	t.deepEqual(queryString.parse('nums=1,2,3&single=10', {
+		arrayFormat: 'comma',
+		types: {
+			nums: value => Number(value) * 3,
+			single: value => Number(value) * 2,
+		},
+	}), {
+		nums: [3, 6, 9],
+		single: 20,
+	});
+});