77 lines
1.9 KiB
JavaScript
77 lines
1.9 KiB
JavaScript
/**
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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 objectKeys = require( './../../keys' );
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var isFunction = require( '@stdlib/assert/is-function' );
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// MAIN //
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/**
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* Returns a partial object copy containing properties for which a predicate returns a truthy value.
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*
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* @param {Object} obj - source object
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* @param {Function} predicate - predicate function
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* @throws {TypeError} first argument must be an object
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* @throws {TypeError} second argument must be a function
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* @returns {Object} new object
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*
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* @example
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* function predicate( key, value ) {
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* return ( value > 1 );
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* }
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*
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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 = pickBy( obj1, predicate );
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* // returns { 'b': 2 }
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*/
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function pickBy( obj, predicate ) {
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var 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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if ( !isFunction( predicate ) ) {
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throw new TypeError( 'invalid argument. Second argument must be a function. Value: `'+predicate+'`.' );
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}
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out = {};
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keys = objectKeys( obj );
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for ( i = 0; i < keys.length; i++ ) {
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key = keys[ i ];
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if ( predicate( key, 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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// EXPORTS //
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module.exports = pickBy;
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