Answers for "js array reduce"

javascript sum of array

const sum = arr => arr.reduce((a, b) => a + b, 0);

javascript reduce promises

const sum = await [
  Promise.resolve(1),
  Promise.resolve(1),
  Promise.resolve(1)
].reduce(async (previousPromise, itemPromise) => {
  const sum = await previousPromise;
  const item = await itemPromise;
  return sum + item;
}, Promise.resolve(0))

// sum === 3

javascript reduce

var array = [36, 25, 6, 15];

array.reduce(function(accumulator, currentValue) {
  return accumulator + currentValue;
}, 0); // 36 + 25 + 6 + 15 = 82

how to use reduce in javascript

const sum = array.reduce((accumulator, element) => {
  return accumulator + element;
}, 0);
// An example that will loop through an array adding
// each element to an accumulator and returning it
// The 0 at the end initializes accumulator to start at 0
// If array is [2, 4, 6], the returned value in sum
// will be 12 (0 + 2 + 4 + 6)

const product = array.reduce((accumulator, element) => {
  return accumulator * element;
}, 1);
// Multiply all elements in array and return the total
// Initialize accumulator to start at 1
// If array is [2, 4, 6], the returned value in product
// will be 48 (1 * 2 * 4 * 6)

js reduce

// syntax: array.reduce(function, accumulator-initial-value)
let array = [3, 7, 2, 9, 5]
const result = array.reduce((accumulator, currentValue, currentIndex, arr) => {
  // code
}, initialValue)

// accumulator = will store return value of the function
// currentValue = iterate through each array element
// currentIndex = index of currentValue
// arr = original array
// initialValue = set accumulator initial value

javascript reduce

[3, 2.1, 5, 8].reduce((total, number) => total + number, 0)

// loop 1: 0 + 3
// loop 2: 3 + 2.1
// loop 3: 5.1 + 5
// loop 4: 10.1 + 8
// returns 18.1