Example 1: how to use reduce 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)
Example 2: reduce
// Array.prototype.reduce()
const array1 = [1, 2, 3, 4];
const reducer = (accumulator, currentValue) => accumulator + currentValue;
// 1 + 2 + 3 + 4
console.log(array1.reduce(reducer));
// expected output: 10
// 5 + 1 + 2 + 3 + 4
console.log(array1.reduce(reducer, 5));
// expected output: 15
Example 3: reduce()
const array1 = [1, 2, 3, 4];
const reducer = (accumulator, currentValue) => accumulator + currentValue;
// 1 + 2 + 3 + 4
console.log(array1.reduce(reducer));
// expected output: 10
// 5 + 1 + 2 + 3 + 4
console.log(array1.reduce(reducer, 5));
// expected output: 15
Example 4: reduce
var sum = _.reduce([1, 2, 3], function(memo, num){ return memo + num; }, 0);
=> 6
Example 5: reduce method
The reduce() method executes a reducer function (that you provide) on each element of the array, resulting in single output value.
The reducer function takes four arguments:
Accumulator (acc)
Current Value (cur)
Current Index (idx)
Source Array (src)
//syntax
arr.reduce(callback( accumulator, currentValue, [, index[, array]] )[, initialValue])
//example flatten an array
let flattened = [[0, 1], [2, 3], [4, 5]].reduce(
( accumulator, currentValue ) => accumulator.concat(currentValue),
[]
)