extname.js (1291B)
1 /** 2 * @license Apache-2.0 3 * 4 * Copyright (c) 2018 The Stdlib Authors. 5 * 6 * Licensed under the Apache License, Version 2.0 (the "License"); 7 * you may not use this file except in compliance with the License. 8 * You may obtain a copy of the License at 9 * 10 * http://www.apache.org/licenses/LICENSE-2.0 11 * 12 * Unless required by applicable law or agreed to in writing, software 13 * distributed under the License is distributed on an "AS IS" BASIS, 14 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 15 * See the License for the specific language governing permissions and 16 * limitations under the License. 17 */ 18 19 'use strict'; 20 21 // MODULES // 22 23 var isString = require( '@stdlib/assert/is-string' ).isPrimitive; 24 var RE_EXTNAME = require( '@stdlib/regexp/extname' ).REGEXP; 25 26 27 // MAIN // 28 29 /** 30 * Returns a filename extension. 31 * 32 * @param {string} filename - filename 33 * @throws {TypeError} must provide a string primitive 34 * @returns {string} filename extension 35 * 36 * @example 37 * var ext = extname( 'index.js' ); 38 * // returns '.js' 39 */ 40 function extname( filename ) { 41 if ( !isString( filename ) ) { 42 throw new TypeError( 'invalid argument. Filename must be a primitive string. Value: `' + filename + '`.' ); 43 } 44 return RE_EXTNAME.exec( filename )[ 1 ]; 45 } 46 47 48 // EXPORTS // 49 50 module.exports = extname;