time-to-botec

deepmerge.js (3389B)

---

 /**
 * @license Apache-2.0
 *
 * Copyright (c) 2018 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 objectKeys = require( './../../keys' );
 var isObject = require( '@stdlib/assert/is-object' );
 var hasOwnProp = require( '@stdlib/assert/has-own-property' );
 var isBuffer = require( '@stdlib/assert/is-buffer' );
 var isFunction = require( '@stdlib/assert/is-function' );
 var typeOf = require( './../../type-of' );
 var deepCopy = require( './../../copy' );
 
 
 // MAIN //
 
 /**
 * Merges a source object into a target object.
 *
 * @private
 * @param {Object} target - target object
 * @param {Object} source - source object
 * @param {number} level - merge level
 * @param {boolean} copy - indicates whether to perform a deep copy of merged values
 * @param {(boolean|Function)} override - defines the merge strategy
 * @param {boolean} extend - indicates whether new properties can be added to the target object
 */
 function deepMerge( target, source, level, copy, override, extend ) {
 	var hasProp;
 	var isFunc;
 	var name;
 	var keys;
 	var curr;
 	var key;
 	var val;
 	var tmp;
 	var i;
 
 	// Determine if we were provided a custom override strategy:
 	isFunc = isFunction( override );
 
 	// Decrement the level:
 	level -= 1;
 
 	// Loop through the source keys and implement the merge strategy...
 	keys = objectKeys( source );
 	for ( i = 0; i < keys.length; i++ ) {
 		key = keys[ i ];
 		hasProp = hasOwnProp( target, key );
 
 		// Can we add new properties to the target?
 		if ( !hasProp && !extend ) {
 			continue;
 		}
 		val = source[ key ];
 
 		if ( hasProp ) {
 			curr = target[ key ];
 			name = typeOf( curr );
 
 			// Should we recurse to perform a deep(er) merge? (only if both the current value and the proposed value are objects and the level is > 0)
 			if (
 				!isBuffer( curr ) &&
 				name === 'object' &&
 				isObject( val ) &&
 				level
 			) {
 				deepMerge( curr, val, level, copy, override, extend );
 				continue;
 			}
 			// Should we apply a custom merge (override) strategy?
 			if ( isFunc ) {
 				tmp = override( curr, val, key );
 
 				// WARNING: the following check does NOT prevent shared (leaky) nested references. We only check for top-level reference equality. We will assume that the user knows best, given their having provided a custom override strategy.
 				if ( copy && tmp !== curr && tmp === val ) {
 					tmp = deepCopy( tmp );
 				}
 				target[ key ] = tmp;
 			}
 			// Are we allowed to override an existing target value?
 			else if ( override ) {
 				if ( copy ) {
 					target[ key ] = deepCopy( val );
 				} else {
 					target[ key ] = val;
 				}
 			}
 		}
 		// New property to be added to target object. Should we deep copy the source value?
 		else if ( copy ) {
 			target[ key ] = deepCopy( val );
 		}
 		// Perform a simple assignment...
 		else {
 			target[ key ] = val;
 		}
 	}
 }
 
 
 // EXPORTS //
 
 module.exports = deepMerge;