refactor: improve type inference

Author: kgryte

lib/node_modules/@stdlib/string/base/for-each-grapheme-cluster/docs/types/index.d.ts

@@ -23,15 +23,15 @@
 *
 * @returns result
 */
-type Nullary = () => any;
+type Nullary<T> = ( this: T ) => any;
 
 /**
 * Callback invoked for each grapheme cluster (i.e., user-perceived character) in a string.
 *
 * @param value - grapheme cluster
 * @returns result
 */
-type Unary = ( value: string ) => any;
+type Unary<T> = ( this: T, value: string ) => any;
 
 /**
 * Callback invoked for each grapheme cluster (i.e., user-perceived character) in a string.
@@ -40,7 +40,7 @@ type Unary = ( value: string ) => any;
 * @param index - starting grapheme cluster index
 * @returns result
 */
-type Binary = ( value: string, index: number ) => any;
+type Binary<T> = ( this: T, value: string, index: number ) => any;
 
 /**
 * Callback invoked for each grapheme cluster (i.e., user-perceived character) in a string.
@@ -50,7 +50,7 @@ type Binary = ( value: string, index: number ) => any;
 * @param str - input string
 * @returns result
 */
-type Ternary = ( value: string, index: number, str: string ) => any;
+type Ternary<T> = ( this: T, value: string, index: number, str: string ) => any;
 
 /**
 * Callback invoked for each grapheme cluster (i.e., user-perceived character) in a string.
@@ -60,7 +60,7 @@ type Ternary = ( value: string, index: number, str: string ) => any;
 * @param str - input string
 * @returns result
 */
-type Callback = Nullary | Unary | Binary | Ternary;
+type Callback<T> = Nullary<T> | Unary<T> | Binary<T> | Ternary<T>;
 
 /**
 * Invokes a function for each grapheme cluster (i.e., user-perceived character) in a string.
@@ -85,7 +85,7 @@ type Callback = Nullary | Unary | Binary | Ternary;
 *
 * forEach( 'Hello, World!', log );
 */
-declare function forEach( str: string, clbk: Callback, thisArg?: any ): string;
+declare function forEach<T = unknown>( str: string, clbk: Callback<T>, thisArg?: ThisParameterType<Callback<T>> ): string;
 
 
 // EXPORTS //