Syntax, Parameter and Return Value
Syntax:
_.cloneDeep(value)
Parameters:
value (Object|Array): The value to deeply clone.
Return Value:
Returns the deeply cloned value.
Examples
Deep Cloning an Object with Nested Structures:
JavaScript
var _ = require('lodash');
var object = { a: 1, b: { c: 2, d: [3, 4] } };
var clonedObject = _.cloneDeep(object);
clonedObject.b.c = 5;
clonedObject.b.d.push(6);
console.log(object);
console.log(clonedObject);

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Output:
{ a: 1, b: { c: 2, d: [3, 4] } }
{ a: 1, b: { c: 5, d: [3, 4, 6] } }
Demonstrates cloning an object with nested arrays and objects. Changes to the clone do not affect the original.
Deep Cloning Arrays Containing Objects:
JavaScript
var items = [{ id: 1, name: 'Item 1' }, { id: 2, name: 'Item 2' }];
var clonedItems = _.cloneDeep(items);
clonedItems[0].name = 'Updated Item 1';
console.log(items);
console.log(clonedItems);

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Output:
[{ id: 1, name: 'Item 1' }, { id: 2, name: 'Item 2' }]
[{ id: 1, name: 'Updated Item 1' }, { id: 2, name: 'Item 2' }]
Shows how to deep clone an array containing objects, allowing for independent modifications.
Preserving Complex Data Structures:
JavaScript
var complexStructure = {
date: new Date(),
nested: { numbers: [1, 2, 3], flag: true }
};
var clone = _.cloneDeep(complexStructure);
clone.nested.numbers.push(4);
console.log(complexStructure.nested.numbers);
console.log(clone.nested.numbers);

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Output:
[1, 2, 3]
[1, 2, 3, 4]
An example of deep cloning a complex structure with dates and nested objects.
Cloning Objects with Methods:
JavaScript
var person = {
name: 'Alice',
greet: function() { console.log('Hello, ' + this.name); }
};
var clonedPerson = _.cloneDeep(person);
clonedPerson.name = 'Bob';
clonedPerson.greet();
person.greet();

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Output:
'Hello, Bob'
'Hello, Alice'
Demonstrates that methods within objects are also cloned, and the cloned methods reference the cloned data.
Frequently Asked Questions
How does deep cloning differ from shallow cloning?
Deep cloning creates copies of all items within an object or array, including nested structures, ensuring no references to the original data. Shallow cloning only copies the top-level elements.
Does _.cloneDeep() handle all types of data?
_.cloneDeep() effectively clones most data types, including arrays, objects, and primitives. However, it may not handle some special objects (like functions, Map, Set, or circular references) as expected.
Can _.cloneDeep() lead to performance issues?
Deep cloning can be resource-intensive, especially for very large or complex objects. It's important to use it judiciously to avoid performance overhead.
Conclusion
Lodash's _.cloneDeep() method is essential for creating independent copies of complex data structures. It allows for safe modification of cloned data without any impact on the original source, making it invaluable in various programming scenarios.
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