78 lines
2.1 KiB
JavaScript
78 lines
2.1 KiB
JavaScript
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/**
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* @license Apache-2.0
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*
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* Copyright (c) 2018 The Stdlib Authors.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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'use strict';
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// MODULES //
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var isString = require( '@stdlib/assert/is-string' ).isPrimitive;
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var isStringArray = require( '@stdlib/assert/is-string-array' ).primitives;
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var hasOwnProp = require( '@stdlib/assert/has-own-property' );
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// MAIN //
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/**
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* Returns a partial object copy containing only specified keys. If a key does not exist as an own property in a source object, the key is ignored.
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*
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* @param {Object} obj - source object
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* @param {(string|StringArray)} keys - keys to copy
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* @throws {TypeError} first argument must be an object
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* @throws {TypeError} second argument must be either a string or an array of strings
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* @returns {Object} new object
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*
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* @example
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* var obj1 = {
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* 'a': 1,
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* 'b': 2
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* };
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*
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* var obj2 = pick( obj1, 'b' );
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* // returns { 'b': 2 }
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*/
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function pick( obj, keys ) {
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var out;
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var key;
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var i;
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if ( typeof obj !== 'object' || obj === null ) {
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throw new TypeError( 'invalid argument. First argument must be an object. Value: `'+obj+'`.' );
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}
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out = {};
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if ( isString( keys ) ) {
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if ( hasOwnProp( obj, keys ) ) {
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out[ keys ] = obj[ keys ];
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}
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return out;
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}
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if ( isStringArray( keys ) ) {
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for ( i = 0; i < keys.length; i++ ) {
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key = keys[ i ];
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if ( hasOwnProp( obj, key ) ) {
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out[ key ] = obj[ key ];
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}
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}
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return out;
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}
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throw new TypeError( 'invalid argument. Second argument must be either a string primitive or an array of string primitives. Value: `'+keys+'`.' );
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}
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// EXPORTS //
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module.exports = pick;
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