# Find consecutive elements average JavaScript

JavascriptWeb DevelopmentObject Oriented Programming

Let’s say, we have an array of numbers −

const arr = [3, 5, 7, 8, 3, 5, 7, 4, 2, 8, 4, 2, 1];

We are required to write a function that returns an array with the average of the corresponding element and its predecessor. For the first element, as there are no predecessors, so that very element should be returned.

Let’s write the code for this function, we will use the Array.prototype.map() function to solve this problem −

## Example

const consecutiveAverage = arr => {
return arr.map((el, ind, array) => {
return ((el + (array[ind-1] || 0)) / (1 + !!ind));
});
};
console.log(consecutiveAverage(arr));

## Output

The output in the console will be −

[
3, 4, 6, 7.5, 5.5, 4,
6, 5.5, 3, 5, 6, 3,
1.5
]
Published on 26-Aug-2020 11:21:20