reduce javascript

1var array = [36, 25, 6, 15];
2
3array.reduce(function(accumulator, currentValue) {
4  return accumulator + currentValue;
5}, 0); // 36 + 25 + 6 + 15 = 82

1const numbers = [15.5, 2.3, 1.1, 4.7];
2document.getElementById("demo").innerHTML = numbers.reduce(getSum, 0);
3
4function getSum(total, num) {
5  return total + Math.round(num);
6}

1const sum = array.reduce((accumulator, element) => {
2  return accumulator + element;
3}, 0);
4// An example that will loop through an array adding
5// each element to an accumulator and returning it
6// The 0 at the end initializes accumulator to start at 0
7// If array is [2, 4, 6], the returned value in sum
8// will be 12 (0 + 2 + 4 + 6)
9
10const product = array.reduce((accumulator, element) => {
11  return accumulator * element;
12}, 1);
13// Multiply all elements in array and return the total
14// Initialize accumulator to start at 1
15// If array is [2, 4, 6], the returned value in product
16// will be 48 (1 * 2 * 4 * 6)

1function reduce(array, func, seed) {
2  let previousResult;
3  if (seed === undefined) {
4    previousResult = array[0];
5    for (let i = 1; i < array.length; i++) {
6      previousResult = func(previousResult, array[i], i, array);
7    }
8    console.log(previousResult);
9  } else {
10    previousResult = seed;
11    each(array, function(e, i, a) {
12      previousResult = func(previousResult, e, i, array);
13    });
14  }
15  return previousResult;
16};

1/* this is our initial value i.e. the starting point*/
2const initialValue = 0;
3
4/* numbers array */
5const numbers = [5, 10, 15];
6
7/* reducer method that takes in the accumulator and next item */
8const reducer = (accumulator, item) => {
9  return accumulator + item;
10};
11
12/* we give the reduce method our reducer function
13  and our initial value */
14const total = numbers.reduce(reducer, initialValue)
15

1//note idx and sourceArray are optional
2const sum = array.reduce((accumulator, element[, idx[, sourceArray]]) => {
3	//arbitrary example of why idx might be needed
4	return accumulator + idx * 2 + element 
5}, 0);