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Reverse index value sum of array in JavaScript
Suppose we have an array of numbers like this −
const arr = [3, 6, 7, 3, 1, 4, 4, 3, 6, 7];
This array in the example contains 10 elements, so the index of last element happens to be 9. We are required to write a function that takes in one such array and returns the reverse index multiplied sum of the elements.
Like in this example, it would be something like −
(9*3)+(8*6)+(7*7)+(6*3)+.... until the end of the array.
Therefore, let's write the code for this function −
Example
const arr = [3, 6, 7, 3, 1, 4, 4, 3, 6, 7];
const reverseMultiSum = arr => {
return arr.reduce((acc, val, ind) => {
const sum = val * (arr.length - ind - 1);
return acc + sum;
}, 0);
};
console.log(reverseMultiSum(arr));Output
The output in the console will be −
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Updated on: 31-Aug-2020
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