add allowEmptyArrays option

index.js

@@ -96,7 +96,12 @@ function parserForArrayFormat(options) {
 				}
 
 				if (accumulator[key] === undefined) {
-					accumulator[key] = [value];
+					if (options.allowEmptyArrays) {
+						accumulator[key] = [];
+					} else {
+						accumulator[key] = [value];
+					}
+
 					return;
 				}
 
@@ -197,7 +202,8 @@ function parse(input, options) {
 		sort: true,
 		arrayFormat: 'none',
 		parseNumbers: false,
-		parseBooleans: false
+		parseBooleans: false,
+		allowEmptyArrays: false
 	}, options);
 
 	const formatter = parserForArrayFormat(options);
@@ -263,7 +269,8 @@ exports.stringify = (object, options) => {
 	options = Object.assign({
 		encode: true,
 		strict: true,
-		arrayFormat: 'none'
+		arrayFormat: 'none',
+		allowEmptyArrays: false
 	}, options);
 
 	const formatter = encoderForArrayFormat(options);
@@ -295,6 +302,10 @@ exports.stringify = (object, options) => {
 		}
 
 		if (Array.isArray(value)) {
+			if (options.allowEmptyArrays && value.length === 0) {
+				return key + '[]=';
+			}
+
 			return value
 				.reduce(formatter(key), [])
 				.join('&');

test/parse.js

@@ -293,3 +293,9 @@ test('query strings having comma encoded and format option as `comma`', t => {
 		]
 	});
 });
+
+test('should decode empty arrays when allowEmptyArrays is set', t => {
+	t.deepEqual(queryString.parse('a[]=', {allowEmptyArrays: true, arrayFormat: 'bracket'}), {
+		a: []
+	});
+});

test/stringify.js

@@ -259,3 +259,7 @@ test('should ignore both null and undefined when skipNull is set for arrayFormat
 		arrayFormat: 'index'
 	}), 'a[0]=1&a[1]=2&c=1');
 });
+
+test('should encode empty arrays when allowEmptyArrays is set', t => {
+	t.is(queryString.stringify({a: []}, {allowEmptyArrays: true, arrayFormat: 'bracket'}), 'a[]=');
+});