Syntax, Parameter, and Return Value
Syntax:
_.reduce(collection, [iteratee=_.identity], [accumulator])
Parameters:
-
collection (Array|Object): The collection to iterate over.
-
[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:
JavaScript
var _ = require('lodash');
var numbers = [1, 2, 3, 4, 5];
var sum = _.reduce(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.
Concatenating String Elements:
JavaScript
var strings = ['hello', 'world', 'lodash'];
var concatenated = _.reduce(strings, (result, str) => result + ' ' + str, '');
console.log(concatenated);
You can also try this code with Online Javascript Compiler
Output:
'hello world lodash'
Shows concatenation of strings in an array.
Reducing to an Object:
JavaScript
var keyValuePairs = [['a', 1], ['b', 2], ['c', 3]];
var object = _.reduce(keyValuePairs, (result, [key, value]) => {
result[key] = value;
return result;
}, {});
console.log(object);
You can also try this code with Online Javascript Compiler
Output:
{ 'a': 1, 'b': 2, 'c': 3 }
An example of transforming an array of pairs into an object.
Complex Reduction with Nested Structures:
JavaScript
var collections = [{ 'count': 5 }, { 'count': 10 }, { 'count': 15 }];
var totalCount = _.reduce(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.
Frequently Asked Questions
How does _.reduce() differ from native JavaScript Array.reduce()?
Lodash's _.reduce() works with arrays, objects, and even strings, providing more flexibility than the native Array.reduce(), which is limited to arrays.
What happens if the accumulator is not provided in _.reduce()?
If an accumulator is not provided, _.reduce() uses the first element of the collection as the initial accumulator and starts iteration from the second element.
Is _.reduce() efficient for large collections?
_.reduce() is efficient for most collections, but its performance depends on the complexity of the iteratee function and the size of the collection.
Conclusion
Lodash's _.reduce() method is a powerful tool for accumulating values from a collection. It provides a streamlined and expressive way to iterate over a collection and combine its elements into a single result, making it indispensable for various data transformation tasks.
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