123 lines
3.0 KiB
JavaScript
123 lines
3.0 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 isArray = require( '@stdlib/assert/is-array' );
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var isObject = require( '@stdlib/assert/is-plain-object' );
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var isObjectLike = require( '@stdlib/assert/is-object-like' );
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var isBoolean = require( '@stdlib/assert/is-boolean' ).isPrimitive;
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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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* Inverts an object, such that keys become values and values become keys.
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*
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* @param {ObjectLike} obj - input object
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* @param {Options} [opts] - function options
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* @param {boolean} [opts.duplicates=true] - boolean indicating whether to store duplicate keys
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* @throws {TypeError} first argument must be object-like
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* @throws {TypeError} second argument must an an object
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* @throws {TypeError} must provide valid options
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* @returns {Object} inverted object
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*
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* @example
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* var out = invert({
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* 'a': 'beep',
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* 'b': 'boop'
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* });
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* // returns { 'beep': 'a', 'boop': 'b' }
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*
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* @example
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* var out = invert({
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* 'a': 'beep',
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* 'b': 'beep'
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* });
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* // returns { 'beep': [ 'a', 'b' ] }
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*
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* @example
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* var obj = {};
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* obj.a = 'beep';
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* obj.b = 'boop';
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* obj.c = 'beep'; // inserted after `a`
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*
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* var out = invert( obj, {
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* 'duplicates': false
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* });
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* // returns { 'beep': 'c', 'boop': 'b' }
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*/
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function invert( obj, opts ) {
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var allowDupes = true;
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var keys;
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var len;
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var key;
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var val;
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var out;
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var v;
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var i;
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if ( !isObjectLike( obj ) ) {
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throw new TypeError( 'invalid argument. First argument must be object-like. Value: `' + obj + '`.' );
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}
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if ( arguments.length > 1 ) {
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if ( !isObject( opts ) ) {
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throw new TypeError( 'invalid argument. Options arguments must be an object. Value: `' + opts + '`.' );
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}
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if ( hasOwnProp( opts, 'duplicates' ) ) {
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allowDupes = opts.duplicates;
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if ( !isBoolean( allowDupes ) ) {
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throw new TypeError( 'invalid argument. `duplicates` option must be a boolean primitive. Option: `' + allowDupes + '`.' );
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}
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}
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}
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keys = objectKeys( obj );
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len = keys.length;
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out = {};
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if ( allowDupes ) {
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for ( i = 0; i < len; i++ ) {
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key = keys[ i ];
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val = obj[ key ];
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if ( !hasOwnProp( out, val ) ) {
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out[ val ] = key;
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continue;
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}
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v = out[ val ];
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if ( isArray( v ) ) {
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out[ val ].push( key );
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} else {
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out[ val ] = [ v, key ];
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}
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}
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} else {
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for ( i = 0; i < len; i++ ) {
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key = keys[ i ];
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out[ obj[ key ] ] = 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 = invert;
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