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# lodash._basecopy
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lodash._basecopy is a standalone modular package that provides lodash's internal `baseCopy` utility function. This low-level utility copies properties from a source object to a target object based on an array of property names, serving as a foundational building block for other lodash functions like _.assign and _.defaults.
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## Package Information
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- **Package Name**: lodash._basecopy
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- **Package Type**: npm
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- **Language**: JavaScript
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- **Installation**: `npm install lodash._basecopy`
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## Core Imports
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```javascript
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var baseCopy = require('lodash._basecopy');
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```
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For AMD:
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```javascript
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define(['lodash._basecopy'], function(baseCopy) {
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  // use baseCopy
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});
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```
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## Basic Usage
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```javascript
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var baseCopy = require('lodash._basecopy');
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// Copy specific properties from source to a new object
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var source = { name: 'Alice', age: 30, city: 'New York', country: 'USA' };
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var result = baseCopy(source, ['name', 'age']);
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console.log(result); // { name: 'Alice', age: 30 }
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// Copy properties to an existing target object
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var target = { role: 'developer' };
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baseCopy(source, target, ['name', 'city']);
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console.log(target); // { role: 'developer', name: 'Alice', city: 'New York' }
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```
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## Capabilities
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### Property Copying
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Copies the properties of `source` to `object` based on the specified property names.
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```javascript { .api }
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/**
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 * Copies the properties of `source` to `object`.
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 * 
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 * @param {Object} source The object to copy properties from.
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 * @param {Object} [object={}] The object to copy properties to.
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 * @param {Array} props The property names to copy.
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 * @returns {Object} Returns `object`.
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 */
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function baseCopy(source, object, props);
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```
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**Parameters:**
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- `source` (Object): The object to copy properties from
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- `object` (Object, optional): The object to copy properties to. If not provided, a new empty object is created
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- `props` (Array): The property names to copy as an array of strings
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**Returns:**
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- (Object): Returns the `object` parameter (or newly created object if `object` was not provided)
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**Usage Patterns:**
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Two-parameter usage (creates new target object):
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```javascript
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var result = baseCopy(sourceObj, ['prop1', 'prop2']);
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```
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Three-parameter usage (copies to existing target object):
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```javascript
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var result = baseCopy(sourceObj, targetObj, ['prop1', 'prop2']);
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```
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**Implementation Details:**
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- If the `object` parameter is not provided, the function treats the second parameter as `props` and creates a new empty object as the target
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- Properties are copied using direct assignment (`object[key] = source[key]`)
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- Only copies properties that exist in the `props` array
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- Does not perform deep copying - only copies the property values directly
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- If a property doesn't exist on the source object, `undefined` will be assigned to the target object
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**Examples:**
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```javascript
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var baseCopy = require('lodash._basecopy');
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// Example 1: Basic property copying
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var user = { id: 1, name: 'John', email: 'john@example.com', password: 'secret' };
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var publicUser = baseCopy(user, ['id', 'name', 'email']);
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// Result: { id: 1, name: 'John', email: 'john@example.com' }
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// Example 2: Copying to existing object
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var config = { theme: 'dark' };
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var defaults = { timeout: 5000, retries: 3, theme: 'light' };
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baseCopy(defaults, config, ['timeout', 'retries']);
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// config is now: { theme: 'dark', timeout: 5000, retries: 3 }
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// Example 3: Handling non-existent properties
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var source = { a: 1, b: 2 };
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var result = baseCopy(source, ['a', 'b', 'c']);
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// Result: { a: 1, b: 2, c: undefined }
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```