prepend_object.js (1426B)
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 // MAIN // 22 23 /** 24 * Adds elements from a collection to the beginning of an array-like object. 25 * 26 * @private 27 * @param {Object} obj - input array-like object 28 * @param {ArrayLike} items - items to add 29 * @returns {Object} input object 30 * 31 * @example 32 * var obj = { 33 * 'length': 2, 34 * '0': 1.0, 35 * '1': 2.0 36 * }; 37 * 38 * obj = prepend( obj, [ 3.0, 4.0 ] ); 39 * // returns { 'length': 4, '0': 3.0, '1': 4.0, '2': 1.0, '3': 2.0 } 40 */ 41 function prepend( obj, items ) { 42 var len; 43 var n; 44 var i; 45 46 len = obj.length; 47 n = items.length; 48 49 // Shift all existing elements to the right... 50 for ( i = len-1; i >= 0; i-- ) { 51 obj[ i+n ] = obj[ i ]; 52 } 53 // Add new elements... 54 for ( i = 0; i < n; i++ ) { 55 obj[ i ] = items[ i ]; 56 } 57 obj.length = len + n; 58 return obj; 59 } 60 61 62 // EXPORTS // 63 64 module.exports = prepend;