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Table of contents
1.
Introduction
2.
Why This Function is Used
3.
Syntax, Parameter and Return Value
3.1.
Syntax: 
3.2.
Parameters:
3.3.
Return Value: 
4.
Examples 
4.1.
Comparing Complex Objects:
4.2.
JavaScript
4.3.
Checking Equality of Arrays:
4.4.
JavaScript
4.5.
Differentiating Between Similar-looking Values:
4.6.
JavaScript
4.7.
Use in Conditional Logic:
5.
Frequently Asked Questions
5.1.
How does _.isEqual() handle circular references?
5.2.
Is _.isEqual() efficient for large data structures?
5.3.
Can _.isEqual() compare function properties?
6.
Conclusion
Last Updated: Mar 27, 2024
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Lodash _.isEqual() Method

Author Riya Singh
0 upvote
Roadmap to SDE career at Amazon
Speaker
Anubhav Sinha
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25 Jun, 2024 @ 01:30 PM

Introduction

In JavaScript, comparing complex objects and arrays for equality is a nuanced task, especially when dealing with deeply nested structures. Lodash's _.isEqual() method offers a powerful solution by performing a deep comparison between two values to determine if they are equivalent. 

Lodash _.isEqual() Method

This method is invaluable in scenarios where a thorough and accurate comparison of data structures is required, such as in state management, data validation, or when working with complex JSON objects.

Why This Function is Used

The _.isEqual() function is used for deep comparison of values, including objects and arrays. Unlike the strict equality operator (===) in JavaScript, which only checks for shallow equality, _.isEqual() recursively compares the contents of the values. This deep comparison is crucial for accurately determining the equivalence of complex data structures that may appear similar at the surface level but differ in their nested properties or elements.

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Syntax, Parameter and Return Value

Syntax: 

_.isEqual(value, other)

Parameters:

  • value: The value to compare.
     
  • other: The other value to compare.

Return Value: 

(boolean) - Returns true if the values are equivalent, else false.

Examples 

Comparing Complex Objects:

  • JavaScript

JavaScript

var _ = require('lodash');

var object1 = { a: 1, b: { c: 2 } };

var object2 = { a: 1, b: { c: 2 } };

console.log(_.isEqual(object1, object2));

Output: 

true


Demonstrates the deep comparison of two objects with nested structures.

Checking Equality of Arrays:

  • JavaScript

JavaScript

var array1 = [1, [2, 3]];

var array2 = [1, [2, 3]];

console.log(_.isEqual(array1, array2));

 Output: 

true


Shows deep comparison of arrays, including nested arrays.

Differentiating Between Similar-looking Values:

  • JavaScript

JavaScript

var obj1 = { a: 1, b: 2 };

var obj2 = { a: 1, b: '2' };

console.log(_.isEqual(obj1, obj2));

Output: 

false


An example of how _.isEqual() can differentiate between values that look similar but have different types.

Use in Conditional Logic:

function updateData(newData, oldData) {
  if (!_.isEqual(newData, oldData)) {
    // Perform update
  }
}


Demonstrates using _.isEqual() in conditional logic to check if data has changed before performing an update.

Frequently Asked Questions

How does _.isEqual() handle circular references?

_.isEqual() can handle circular references in objects or arrays. It smartly tracks visited objects and arrays to avoid infinite loops in circular structures.

Is _.isEqual() efficient for large data structures?

While _.isEqual() is designed to be comprehensive, its deep comparison nature can be computationally intensive for very large or deeply nested structures. It should be used judiciously in performance-critical applications.

Can _.isEqual() compare function properties?

_.isEqual() compares function properties by reference, not by their internal structure or context. Two function properties are considered equal if they reference the same function.

Conclusion

Lodash's _.isEqual() method provides a robust solution for deep comparison of objects, arrays, and other complex data structures in JavaScript. It ensures accurate and comprehensive equality checks, far beyond what shallow comparison techniques can offer.

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