What will the output be for console.log(arr.reduce(reducer)) if arr is [1, 4, 9, 16]?

What will the output be for console.log(arr.reduce(reducer)) if arr is [1, 4, 9, 16]?

• A. 30
• B. 16
• C. 10
• D. NaN

Answer: (A)

To determine the output of `console.log(arr.reduce(reducer))` where `arr` is `[1, 4, 9, 16]`, it's important to first understand how the `reduce` method works in JavaScript. The `reduce()` method executes a reducer function (the function provided as the first argument) on each element of the array, resulting in a single output value. The reducer function receives two arguments: an accumulator (which accumulates the results) and the current value being processed in the array. If the reducer function is not explicitly provided, the default behavior of `reduce()` will be to sum the values of the array when using the typical reducer function that adds the current value to the accumulator. In this case, if we assume the `reducer` is a typical addition function, it would look like this: ```javascript function reducer(accumulator, currentValue) { return accumulator + currentValue; } ``` By applying the reducer function step by step: 1. Start with the first element (1) as the initial value of the accumulator. 2. Add the next element (4): 1 + 4 = 5. 3. Add the next element (9): 5 +

To determine the output of console.log(arr.reduce(reducer)) where arr is [1, 4, 9, 16], it's important to first understand how the reduce method works in JavaScript.

The reduce() method executes a reducer function (the function provided as the first argument) on each element of the array, resulting in a single output value. The reducer function receives two arguments: an accumulator (which accumulates the results) and the current value being processed in the array.

If the reducer function is not explicitly provided, the default behavior of reduce() will be to sum the values of the array when using the typical reducer function that adds the current value to the accumulator.

In this case, if we assume the reducer is a typical addition function, it would look like this:

function reducer(accumulator, currentValue) {

return accumulator + currentValue;

}

By applying the reducer function step by step:

1. Start with the first element (1) as the initial value of the accumulator.

2. Add the next element (4): 1 + 4 = 5.

3. Add the next element (9): 5 +