papply.js (1849B)
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 isFunction = require( '@stdlib/assert/is-function' ); 24 25 26 // MAIN // 27 28 /** 29 * Returns a function of smaller arity by partially applying arguments. 30 * 31 * @param {Function} fcn - function to partially apply 32 * @param {...*} [args] - arguments to partially apply 33 * @throws {TypeError} first argument must be a function 34 * @returns {Function} partially applied function 35 * 36 * @example 37 * function add( x, y ) { 38 * return x + y; 39 * } 40 * 41 * var add2 = papply( add, 2 ); 42 * 43 * var sum = add2( 3 ); 44 * // returns 5 45 */ 46 function papply( fcn ) { 47 var pargs; 48 var i; 49 if ( !isFunction( fcn ) ) { 50 throw new TypeError( 'invalid argument. First argument must be a function. Value: `' + fcn + '`.' ); 51 } 52 pargs = new Array( arguments.length-1 ); 53 for ( i = 1; i < arguments.length; i++ ) { 54 pargs[ i-1 ] = arguments[ i ]; 55 } 56 return papplied; 57 58 /** 59 * Partially applied function. 60 * 61 * @private 62 * @param {...*} [args] - function arguments 63 * @returns {*} partially applied function result 64 */ 65 function papplied() { 66 var args; 67 var j; 68 args = pargs.slice(); 69 for ( j = 0; j < arguments.length; j++ ) { 70 args.push( arguments[ j ] ); 71 } 72 return fcn.apply( null, args ); 73 } 74 } 75 76 77 // EXPORTS // 78 79 module.exports = papply;