argument_function.js (1498B)
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 isNonNegativeInteger = require( '@stdlib/assert/is-nonnegative-integer' ).isPrimitive; 24 25 26 // MAIN // 27 28 /** 29 * Returns a function which always returns a specified argument. 30 * 31 * @param {NonNegativeInteger} idx - argument index 32 * @throws {TypeError} must provide a nonnegative integer 33 * @returns {Function} argument function 34 * 35 * @example 36 * var argn = wrap( 1 ); 37 * 38 * var v = argn( 1.0, 2.0, 3.0 ); 39 * // returns 2.0 40 * 41 * v = argn( 'a', 'b', 'c' ); 42 * // returns 'b' 43 * 44 * v = argn( null ); 45 * // returns undefined 46 */ 47 function wrap( idx ) { 48 if ( !isNonNegativeInteger( idx ) ) { 49 throw new TypeError( 'invalid argument. Must provide a nonnegative integer. Value: `'+idx+'`.' ); 50 } 51 return argn; 52 53 /** 54 * Argument function. 55 * 56 * @private 57 * @returns {*} argument 58 */ 59 function argn() { 60 return arguments[ idx ]; 61 } 62 } 63 64 65 // EXPORTS // 66 67 module.exports = wrap;