122 lines
3.3 KiB
JavaScript
122 lines
3.3 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 isObject = require( '@stdlib/assert/is-object' );
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var hasOwnProp = require( '@stdlib/assert/has-own-property' );
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var isBuffer = require( '@stdlib/assert/is-buffer' );
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var isFunction = require( '@stdlib/assert/is-function' );
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var typeOf = require( './../../type-of' );
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var deepCopy = require( './../../copy' );
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// MAIN //
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/**
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* Merges a source object into a target object.
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*
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* @private
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* @param {Object} target - target object
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* @param {Object} source - source object
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* @param {number} level - merge level
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* @param {boolean} copy - indicates whether to perform a deep copy of merged values
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* @param {(boolean|Function)} override - defines the merge strategy
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* @param {boolean} extend - indicates whether new properties can be added to the target object
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*/
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function deepMerge( target, source, level, copy, override, extend ) {
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var hasProp;
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var isFunc;
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var name;
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var keys;
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var curr;
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var key;
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var val;
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var tmp;
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var i;
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// Determine if we were provided a custom override strategy:
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isFunc = isFunction( override );
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// Decrement the level:
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level -= 1;
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// Loop through the source keys and implement the merge strategy...
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keys = objectKeys( source );
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for ( i = 0; i < keys.length; i++ ) {
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key = keys[ i ];
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hasProp = hasOwnProp( target, key );
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// Can we add new properties to the target?
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if ( !hasProp && !extend ) {
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continue;
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}
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val = source[ key ];
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if ( hasProp ) {
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curr = target[ key ];
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name = typeOf( curr );
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// 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)
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if (
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!isBuffer( curr ) &&
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name === 'object' &&
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isObject( val ) &&
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level
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) {
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deepMerge( curr, val, level, copy, override, extend );
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continue;
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}
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// Should we apply a custom merge (override) strategy?
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if ( isFunc ) {
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tmp = override( curr, val, key );
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// 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.
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if ( copy && tmp !== curr && tmp === val ) {
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tmp = deepCopy( tmp );
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}
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target[ key ] = tmp;
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}
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// Are we allowed to override an existing target value?
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else if ( override ) {
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if ( copy ) {
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target[ key ] = deepCopy( val );
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} else {
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target[ key ] = val;
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}
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}
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}
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// New property to be added to target object. Should we deep copy the source value?
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else if ( copy ) {
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target[ key ] = deepCopy( val );
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}
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// Perform a simple assignment...
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else {
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target[ key ] = val;
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}
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}
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}
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// EXPORTS //
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module.exports = deepMerge;
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