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How does the Array.reduce() method work?

Asked on Jul 21, 2025

Answer

The Array.reduce() method in JavaScript is used to reduce an array to a single value by executing a reducer function on each element of the array, from left to right. Here's a simple example:

<!-- BEGIN COPY / PASTE -->
        const numbers = [1, 2, 3, 4];
        const sum = numbers.reduce((accumulator, currentValue) => accumulator + currentValue, 0);
        console.log(sum); // Output: 10
        <!-- END COPY / PASTE -->

Additional Comment:

The "reduce" method takes two arguments: a reducer function and an initial value.
The reducer function itself takes four arguments: "accumulator", "currentValue", "currentIndex", and "array" (only the first two are commonly used).
In the example, the "accumulator" starts at 0 (the initial value) and accumulates the sum of the array elements.
The final result of the "reduce" method is a single value, in this case, the sum of all numbers in the array.

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Ask any question about JavaScript here... and get an instant response.

How does the Array.reduce() method work?

Asked on Jul 21, 2025

Answer

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