feat: Add boolean support

Closes #196.

src/defs.ts

@@ -2,13 +2,14 @@ export type HistoryOptions = 'replace' | 'push'
 
 export type Serializers<T> = {
   parse: (value: string) => T | null
-  serialize: (value: T) => string
+  serialize: (value: T) => string | null
 }
 
 export type QueryTypeMap = {
   string: Serializers<string>
   integer: Serializers<number>
   float: Serializers<number>
+  boolean: Serializers<boolean>
   timestamp: Serializers<Date>
   isoDateTime: Serializers<Date>
 }
@@ -26,6 +27,10 @@ export const queryTypes: QueryTypeMap = {
     parse: v => parseFloat(v),
     serialize: v => v.toString()
   },
+  boolean: {
+    parse: v => Boolean(v) || v === '',
+    serialize: (v: boolean) => (v ? '' : null)
+  },
   timestamp: {
     parse: v => new Date(v),
     serialize: (v: Date) => v.valueOf().toString()

src/useQueryState.ts

@@ -70,11 +70,17 @@ export function useQueryState<T = string>(
       // unnecessary renders when other query parameters change.
       // URLSearchParams is already polyfilled by Next.js
       const query = new URLSearchParams(window.location.search)
-      if (newValue) {
-        query.set(key, serialize(newValue))
-      } else {
+      if (!newValue) {
         // Don't leave value-less keys hanging
         query.delete(key)
+      } else {
+        const serialized = serialize(newValue)
+        if (serialized) {
+          query.set(key, serialized)
+        } else {
+          // Serializers can return null to unset keys
+          query.delete(key)
+        }
       }
 
       // Remove fragment and query from asPath

src/useQueryStates.ts

@@ -96,7 +96,12 @@ export function useQueryStates<T extends object>(
           query.delete(key)
         } else if (newValue !== undefined) {
           const { serialize } = keys[key as keyof T]
-          query.set(key, serialize(newValue as T[keyof T]))
+          const serialized = serialize(newValue as T[keyof T])
+          if (serialized) {
+            query.set(key, serialized)
+          } else {
+            query.delete(key)
+          }
         }
       })