Syntax, Parameter and Return Value
Syntax:
_.reduceRight(collection, [iteratee=_.identity], [accumulator])
Parameters:
-
collection (Array|Object): The collection to iterate over in reverse.
-
[iteratee=_.identity] (Function): The function invoked per iteration.
- [accumulator]: The initial value to start accumulation.
Return Value:
Returns the accumulated value.
Examples
Summing an Array of Numbers in Reverse:
JavaScript
var _ = require('lodash');
var numbers = [1, 2, 3, 4, 5];
var sum = _.reduceRight(numbers, (sum, n) => sum + n, 0);
console.log(sum);
You can also try this code with Online Javascript Compiler
Output:
15
Demonstrates adding up the numbers in an array, starting from the end.
Concatenating String Elements in Reverse Order:
JavaScript
var strings = ['hello', 'world', 'lodash'];
var concatenated = _.reduceRight(strings, (result, str) => result + ' ' + str, '');
console.log(concatenated);
You can also try this code with Online Javascript Compiler
Output:
'lodash world hello'
Shows concatenation of strings in an array, starting from the last element.
Complex Reduction with Nested Structures:
JavaScript
var collections = [{ 'count': 5 }, { 'count': 10 }, { 'count': 15 }];
var totalCount = _.reduceRight(collections, (sum, obj) => sum + obj.count, 0);
console.log(totalCount);
You can also try this code with Online Javascript Compiler
Output:
30
Demonstrates summing values from a collection of objects in reverse order.
Building a Nested Structure in Reverse:
JavaScript
var nestedArrays = [[1, 2], [3, 4], [5, 6]];
var nestedStructure = _.reduceRight(nestedArrays, (result, array) => [array, result], []);
console.log(JSON.stringify(nestedStructure));
You can also try this code with Online Javascript Compiler
Output:
"[[5,6],[[3,4],[[1,2],[]]]]"
An example of building a nested array structure in reverse.
Frequently Asked Questions
How does _.reduceRight() differ from _.reduce()?
While _.reduce() iterates from the start to the end of a collection, _.reduceRight() performs the iteration in reverse, from the end to the start.
Can _.reduceRight() be used with non-array collections?
Yes, it can be used with objects, but it's most commonly and effectively used with arrays, especially when the order of elements is significant.
Is _.reduceRight() efficient for large collections?
_.reduceRight() is generally efficient, but its performance depends on the complexity of the iteratee function and the size of the collection.
Conclusion
Lodash's _.reduceRight() method is a functional and efficient way to accumulate values from a collection in reverse order. It provides a flexible approach to perform reduction operations on collections, especially useful in scenarios where the processing order is crucial.
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