Syntax, Parameter and Return Value
Syntax:
_.reject(collection, [predicate=_.identity])
Parameters:
-
collection (Array|Object): The collection to iterate over.
- [predicate=_.identity] (Function): The function invoked per iteration.
Return Value:
(Array) - Returns the new array of filtered elements.
Examples
Rejecting Based on a Simple Condition:
JavaScript
var _ = require('lodash');
var numbers = [1, 2, 3, 4, 5, 6];
var rejectedNumbers = _.reject(numbers, n => n % 2 === 0);
console.log(rejectedNumbers);
You can also try this code with Online Javascript Compiler
Output:
[1, 3, 5]
Demonstrates rejecting even numbers from an array.
Filtering Out Objects with a Specific Property:
JavaScript
var users = [{ 'user': 'barney', 'active': false },
{ 'user': 'fred', 'active': true },
{ 'user': 'pebbles', 'active': false }];
var inactiveUsers = _.reject(users, 'active');
console.log(inactiveUsers);
You can also try this code with Online Javascript Compiler
Output:
[{ 'user': 'barney', 'active': false }, { 'user': 'pebbles', 'active': false }]
Shows rejecting objects where the active property is true.
Using a Complex Predicate Function:
JavaScript
var items = [{ 'name': 'apple', 'weight': 0.5 },
{ 'name': 'banana', 'weight': 0.3 },
{ 'name': 'cucumber', 'weight': 1 }];
var heavyItems = _.reject(items, item => item.weight <= 0.5);
console.log(heavyItems);
You can also try this code with Online Javascript Compiler
Output:
[{ 'name': 'cucumber', 'weight': 1 }]
An example of rejecting items based on their weight.
Rejecting Strings in an Array:
JavaScript
var strings = ['hello', 'world', 'lodash', 'javascript'];
var shortStrings = _.reject(strings, s => s.length > 5);
console.log(shortStrings);
You can also try this code with Online Javascript Compiler
Output:
['hello', 'world']
Demonstrates rejecting strings based on their length.
Frequently Asked Questions
How does _.reject() differ from _.filter()?
_.reject() returns an array of elements for which the predicate returns false, whereas _.filter() returns elements for which the predicate returns true.
Can _.reject() be used with non-array collections?
Yes, _.reject() can be used with objects, but it's most commonly used with arrays.
Is _.reject() efficient for large datasets?
_.reject() is generally efficient for large datasets, but performance can vary depending on the complexity of the predicate function.
Conclusion
Lodash's _.reject() method provides a straightforward and efficient way to filter out elements from a collection that do not meet a specific criterion. It's a valuable tool for data manipulation, allowing developers to easily exclude unwanted elements from their datasets.
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