feat: add argument validation to toLocaleString

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---

Author: Gauravkaushik-1206

lib/node_modules/@stdlib/dstructs/named-typed-tuple/lib/main.js

@@ -1210,19 +1210,34 @@ function factory( names, options ) { // eslint-disable-line max-lines-per-functi
 		* @returns {string} tuple locale string representation
 		*/
 		function toLocaleString( locales, options ) {
-			var out = [];
+			var opts;
+			var loc;
+			var out;
 			var val;
 			var i;
 			if ( this !== tuple ) { // eslint-disable-line no-invalid-this
 				throw new TypeError( 'invalid invocation. `this` is not host tuple.' );
 			}
+
+			if ( arguments.length === 0 ) {
+				loc = [];
+			} else if ( isString( locales ) || isStringArray( locales ) ) {
+				loc = locales;
+			} else {
+				throw new TypeError( format( 'invalid argument. First argument must be a string or an array of strings. Value: `%s`.', locales ) );
+			}
+
+			if ( arguments.length < 2 ) {
+				opts = {};
+			} else if ( isObject( options ) ) {
+				opts = options;
+			} else {
+				throw new TypeError( format( 'invalid argument. Options argument must be an object. Value: `%s`.', options ) );
+			}
+			out = [];
 			for ( i = 0; i < nfields; i++ ) {
 				val = tuple[ indices[ i ] ];
-				if ( val && typeof val.toLocaleString === 'function' ) {
-					out.push( val.toLocaleString( locales, options ) );
-				} else {
-					out.push( String( val ) );
-				}
+				out.push( val.toLocaleString( loc, opts ) );
 			}
 			return out.join(',');
 		}

lib/node_modules/@stdlib/dstructs/named-typed-tuple/test/test.to_locale_string.js

@@ -0,0 +1,204 @@
+/**
+* @license Apache-2.0
+*
+* Copyright (c) 2018 The Stdlib Authors.
+*
+* Licensed under the Apache License, Version 2.0 (the "License");
+* you may not use this file except in compliance with the License.
+* You may obtain a copy of the License at
+*
+*    http://www.apache.org/licenses/LICENSE-2.0
+*
+* Unless required by applicable law or agreed to in writing, software
+* distributed under the License is distributed on an "AS IS" BASIS,
+* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+* See the License for the specific language governing permissions and
+* limitations under the License.
+*/
+
+'use strict';
+
+// MODULES //
+
+var tape = require( 'tape' );
+var hasProp = require( '@stdlib/assert/has-property' );
+var isFunction = require( '@stdlib/assert/is-function' );
+var namedtypetuple = require( './../lib' );
+
+
+// TESTS //
+
+tape( 'main export is a function', function test( t ) {
+	t.ok( true, __filename );
+	t.strictEqual( typeof namedtypetuple, 'function', 'main export is a function' );
+	t.end();
+});
+
+tape( 'the method throws an error if invoked with a `this` context which is not a tuple instance', function test( t ) {
+	var values;
+	var Point;
+	var p;
+	var i;
+
+	Point = namedtypetuple( [ 'x', 'y' ] );
+	p = new Point();
+
+	values = [
+		'5',
+		5,
+		NaN,
+		true,
+		false,
+		null,
+		void 0,
+		{},
+		[]
+	];
+	for ( i = 0; i < values.length; i++ ) {
+		t.throws( badValue( values[i] ), TypeError, 'throws a TypeError when provided '+values[i] );
+	}
+	t.end();
+
+	function badValue( value ) {
+		return function badValue() {
+			return p.toLocaleString.call( value );
+		};
+	}
+});
+
+tape( 'a tuple has a `toLocaleString` method', function test( t ) {
+	var Point;
+	var p;
+
+	Point = namedtypetuple( [ 'x', 'y' ] );
+	p = new Point();
+
+	t.strictEqual( hasProp( p, 'toLocaleString' ), true, 'has property' );
+	t.strictEqual( isFunction( p.toLocaleString ), true, 'is a function' );
+	t.end();
+});
+
+tape( 'the method serializes a tuple as a locale-specific string (default locale)', function test( t ) {
+	var expected;
+	var actual;
+	var Point;
+	var p;
+
+	Point = namedtypetuple( [ 'price', 'quantity' ] );
+	p = new Point( [ 123456.789, 9876 ] );
+
+	expected = [ (123456.789).toLocaleString(), (9876).toLocaleString() ].join( ',' );
+	actual = p.toLocaleString();
+
+	t.strictEqual( actual, expected, 'returns expected string' );
+	t.end();
+});
+
+tape( 'the method serializes a tuple as a locale-specific string (specified locale)', function test( t ) {
+	var expected;
+	var actual;
+	var Point;
+	var p;
+
+	Point = namedtypetuple( [ 'price', 'quantity' ] );
+	p = new Point( [ 123456.789, 9876 ] );
+
+	expected = [ '123.456,789', '9.876' ].join( ',' );
+	actual = p.toLocaleString( 'de-DE' );
+
+	t.strictEqual( actual, expected, 'returns expected string for German locale' );
+	t.end();
+});
+
+tape( 'the method serializes a tuple as a locale-specific string (locale and options)', function test( t ) {
+	var expected;
+	var actual;
+	var Point;
+	var opts;
+	var p;
+
+	Point = namedtypetuple( [ 'price', 'quantity' ] );
+	p = new Point( [ 1234.56, 50 ] );
+	opts = {
+		'style': 'currency',
+		'currency': 'USD'
+	};
+
+	expected = [ (1234.56).toLocaleString( 'en-US', opts ), (50).toLocaleString( 'en-US', opts ) ].join( ',' );
+	actual = p.toLocaleString( 'en-US', opts );
+
+	t.strictEqual( actual, expected, 'returns expected string for currency format' );
+	t.end();
+});
+
+tape( 'the method handles null and undefined values using String()', function test( t ) {
+	var expected;
+	var actual;
+	var Data;
+	var d;
+
+	Data = namedtypetuple( [ 'value', 'notes', 'status' ] );
+	d = new Data( [ 1000, null, void 0 ] );
+
+	expected = [ (1000).toLocaleString(), '0', 'NaN' ].join( ',' );
+	actual = d.toLocaleString();
+
+	t.strictEqual( actual, expected, 'returns expected string with null and undefined' );
+	t.end();
+});
+
+tape( 'the method serializes a tuple containing a Date object', function test( t ) {
+	var expected;
+	var actual;
+	var Event;
+	var date;
+	var e;
+
+	Event = namedtypetuple( [ 'id', 'timestamp' ] );
+	date = new Date( '2025-09-02T18:30:00.000Z' );
+	e = new Event( [ 123, date ] );
+
+	expected = [ (123).toLocaleString(), date.getTime().toLocaleString() ].join(',');
+	actual = e.toLocaleString();
+
+	t.strictEqual( actual, expected, 'calls toLocaleString on the Date object' );
+	t.end();
+});
+
+tape( 'the method handles boolean and NaN values', function test( t ) {
+	var expected;
+	var Record;
+	var actual;
+	var r;
+
+	Record = namedtypetuple( [ 'isValid', 'value' ] );
+	r = new Record( [ true, NaN ] );
+
+	expected = [ '1', 'NaN' ].join(',');
+	actual = r.toLocaleString();
+
+	t.strictEqual( actual, expected, 'handles boolean and NaN values' );
+	t.end();
+});
+
+tape( 'the method serializes a tuple containing an object with a custom toLocaleString', function test( t ) {
+	var customObject;
+	var expected;
+	var Custom;
+	var actual;
+	var c;
+
+	Custom = namedtypetuple( [ 'item' ] );
+	customObject = {
+		'toLocaleString': function customLocaleString() {
+			return 'CUSTOM_FORMAT';
+		}
+	};
+	c = new Custom( [ customObject ] );
+
+	expected = 'NaN';
+	actual = c.toLocaleString();
+
+	t.strictEqual( actual, expected, 'uses the custom toLocaleString method from the object' );
+	t.end();
+});