sum of javascript code example

Example 1: js sum of array

[1, 2, 3, 4].reduce((a, b) => a + b, 0)

// Output: 10

Example 2: javascript sum of array

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

Example 3: add all elements in array javascript

console.log(
  [1, 2, 3, 4].reduce((a, b) => a + b, 0)
)
console.log(
  [].reduce((a, b) => a + b, 0)
)

Example 4: reduce method javascript

// Reduce() method executes a callback function that is passed in
// on each element of the array, resulting in single output value.
const array1 = [1, 2, 3, 4];
const callback = (accumulator, currentValue) => accumulator + currentValue;

// 1 + 2 + 3 + 4
console.log(array1.reduce(callback));
// expected output: 10

// 5 + 1 + 2 + 3 + 4
console.log(array1.reduce(callback, 5));
// expected output: 15 because the initial value is 5.

// This is how Reduce works.
// This is a myReduce method which takes a callback and an optional argument 
// of a default accumulator. If myReduce only receives one argument, then 
// myReduce will use the first element as the accumulator.

Array.prototype.myReduce = function(callback, acc) {
    if (!acc) {
        acc = this.shift();
    }
    this.forEach(function(element) {
        acc = callback(acc, element)
    })
    return acc;
}