JavaScript sum array using recursion-CodePudding

My task is to sum elements of an array and add it to second parameter (number) using recursion. Return only gives me last value of sum. I would appreciate any feedback :)

const getArraySum = (numbersArray, initialValue) => {
// let sum = initialValue

// for (let i = 0; i < numbersArray.length; i  ) {
//     sum  = numbersArray[i]
// } return sum
if (numbersArray.length === 0 ) {
    return initialValue 
} else {
    let sum = 0
    sum  = numbersArray[numbersArray.length-1]
    console.log (numbersArray)
    numbersArray.pop()
    console.log (sum)
    getArraySum (numbersArray)
    return sum   initialValue
} 
};

const result1 = getArraySum([4,7,10], 5)
console.log (result1)

CodePudding user response：

You're ignoring the return value of the recursive call to getArraySum. Instead, you should add it to the returned value:

const getArraySum = (numbersArray, initialValue) => {
  if (numbersArray.length === 0) {
      return initialValue 
  } 
  return numbersArray.pop()   getArraySum(numbersArray, initialValue);
};

const result = getArraySum([4,7,10], 5)
console.log (result)

Note that the initialValue should only be taken into consideration once, in the end condition where the array is empty.

CodePudding user response：

The idea is to split an array into head (=the first element or null for an empty array) and tail (everything else). Then, establish that the sum is head sum(tail):

let sum = ([head = null, ...tail]) =>
    head === null ? 0 : head   sum(tail)

console.log(sum([1,2,3,4]))

Having an initial value is a silly requirement, but it goes the same way:

let sum = ([head = null, ...tail], init = 0) =>
    init   (head === null ? 0 : head   sum(tail))


console.log(sum([1, 2, 3, 4], 100))

CodePudding user response：

You could take the single values a summing variable and return immediately if the array is empty.

Otherwise return the function call with a new shorter array and hte sum of sum and the first element.

const
    getSum = (numbers, sum = 0) => {
        if (!numbers.length) return sum;
        return getSum(numbers.slice(1), sum   numbers[0]);
    };

console.log (getSum([4, 7, 10], 5));