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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.
Checking All Numbers for Evenness:
4.2.
JavaScript
4.3.
Validating Object Properties:
4.4.
JavaScript
4.5.
Array of Strings:
4.6.
JavaScript
4.7.
Using Function Shorthand:
4.8.
JavaScript
5.
Frequently Asked Questions 
5.1.
How does _.every() behave with an empty collection?
5.2.
Can _.every() work with collections containing different data types?
5.3.
Is _.every() efficient for large datasets?
6.
Conclusion
Last Updated: Mar 27, 2024
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Lodash _.every() Method

Author Riya Singh
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18 Jun, 2024 @ 01:30 PM

Introduction

Determining if all elements in a collection meet a specific criterion is a common requirement in JavaScript programming. Lodash's _.every() method addresses this need, providing a straightforward way to test whether all elements in an array or object pass a given test. 

Lodash _.every() Method

This article will delve into the functionality of _.every(), covering its syntax, usage, and practical applications with examples and FAQs.

Why This Function is Used

The _.every() function is crucial when a uniform condition needs to be verified across all elements of a collection. This method is widely used in scenarios like data validation, condition checking, and feature toggling, where it's essential to ensure that every element in a dataset conforms to a specific requirement. It enhances code readability and efficiency compared to traditional looping constructs.

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Syntax, Parameter and Return Value

Syntax: 

_.every(collection, [predicate=_.identity])

Parameters:

  • collection (Array|Object): The collection to iterate over.
     
  • [predicate=_.identity] (Function): The function invoked per iteration.

Return Value: 

(boolean) - Returns true if all elements pass the predicate check, else false.

Examples 

Checking All Numbers for Evenness:

  • JavaScript

JavaScript

var _ = require('lodash');

var numbers = [2, 4, 6, 8, 10];

var allEven = _.every(numbers, n => n % 2 === 0);

console.log(allEven);

Output: 

true


This example demonstrates checking if all numbers in an array are even.

Validating Object Properties:

  • JavaScript

JavaScript

var users = [{ 'user': 'barney', 'age': 36, 'active': false },

            { 'user': 'fred', 'age': 40, 'active': false }];

var allInactive = _.every(users, {'active': false});

console.log(allInactive);

Output:

 true


Here, _.every() is used to verify if all objects in an array have a specific property value.

Array of Strings:

  • JavaScript

JavaScript

var words = ['apple', 'amber', 'arc'];

var allStartWithA = _.every(words, w => w.startsWith('a'));

console.log(allStartWithA);

Output: 

true


Checks if every string in an array starts with the letter 'a'.

Using Function Shorthand:

  • JavaScript

JavaScript

var objects = [{ 'n': 4 }, { 'n': 6 }, { 'n': 8 }];

var allGreaterThanThree = _.every(objects, 'n', n => n > 3);

console.log(allGreaterThanThree);

Output:

 true


Utilizing Lodash's shorthand syntax for cleaner and more concise code.

Frequently Asked Questions 

How does _.every() behave with an empty collection?

_.every() returns true for empty collections as there are no elements to fail the predicate test, adhering to the principle of vacuous truth.

Can _.every() work with collections containing different data types?

Yes, but the predicate function must be capable of handling the various data types present in the collection.

Is _.every() efficient for large datasets?

_.every() is efficient for most datasets, but its performance depends on the complexity of the predicate function and the size of the dataset.

Conclusion

Lodash's _.every() method is a concise and effective tool for verifying that all elements in a collection meet a specific criterion. It simplifies the process of uniform condition checking, enhancing both the readability and the reliability of code. This method is an excellent example of how Lodash facilitates more expressive and efficient JavaScript programming.

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