/** * @license Apache-2.0 * * Copyright (c) 2023 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 arraylike2object = require( './../../../base/arraylike2object' ); // VARIABLES // var arraySlice = Array.prototype.slice; // FUNCTIONS // /** * Tests whether an object has a specified method. * * @private * @param {Object} obj - input object * @param {string} method - method name * @returns {boolean} boolean indicating whether an object has a specified method * * @example * var bool = hasMethod( [], 'slice' ); * // returns true * * @example * var bool = hasMethod( [], 'beep' ); * // returns false */ function hasMethod( obj, method ) { return ( typeof obj[ method ] === 'function' ); } /** * Returns a shallow copy of a portion of an array using the `Array#slice` built-in. * * @private * @param {Collection} x - input array * @param {integer} start - starting index (inclusive) * @param {integer} end - ending index (exclusive) * @returns {Array} output array * * @example * var x = [ 1, 2, 3, 4 ]; * * var out = builtin( x, 1, 3 ); * // returns [ 2, 3 ] */ function builtin( x, start, end ) { return arraySlice.call( x, start, end ); } /** * Returns a shallow copy of a portion of an accessor array. * * @private * @param {Object} x - input array object * @param {integer} start - starting index (inclusive) * @param {integer} end - ending index (exclusive) * @returns {Array} output array * * @example * var toAccessorArray = require( '@stdlib/array/base/to-accessor-array' ); * var arraylike2object = require( '@stdlib/array/base/arraylike2object' ); * * var x = arraylike2object( toAccessorArray( [ 1, 2, 3, 4 ] ) ); * * var out = accessors( x, 1, 3 ); * // returns [ 2, 3 ] */ function accessors( x, start, end ) { var data; var get; var out; var i; data = x.data; get = x.accessors[ 0 ]; out = []; for ( i = start; i < end; i++ ) { out.push( get( data, i ) ); } return out; } // MAIN // /** * Returns a shallow copy of a portion of an array. * * @param {Collection} x - input array * @param {integer} start - starting index (inclusive) * @param {integer} end - ending index (exclusive) * @returns {Collection} output array * * @example * var x = [ 1, 2, 3, 4 ]; * * var out = slice( x, 1, 3 ); * // returns [ 2, 3 ] * * var bool = ( out === x ); * // returns false * * @example * var Int32Array = require( '@stdlib/array/int32' ); * * var x = new Int32Array( [ 1, 2, 3, 4 ] ); * * var out = slice( x, 1, 3 ); * // returns [ 2, 3 ] * * var bool = ( out === x ); * // returns false */ function slice( x, start, end ) { var obj; if ( hasMethod( x, 'slice' ) ) { return x.slice( start, end ); } obj = arraylike2object( x ); if ( obj.accessorProtocol ) { return accessors( obj, start, end ); } // Assume we can use the built-in `Array#slice` method to copy elements to a generic array: return builtin( x, start, end ); } // EXPORTS // module.exports = slice;