How to Use Array Reduce Method in JavaScript

What is a reduce operation and how to use array.reduce() method in JavaScript to perform the reduce operation on arrays.

Let’s say you have an array of numbers:

const numbers = [2, 4, 6];

How can you sum these numbers? Thanks to the array.reduce() method of JavaScript, you can easily do that:

const numbers = [2, 4, 6];

const sum = numbers.reduce(function(sum, number) {
  const updatedSum = sum + number;
  return updatedSum;
}, 0);

sum; // 12
  • In this post, you’ll learn about the reduce operation, and how to use array.reduce(callback, initialValue) method to perform the reduce operation on arrays.
  • Reduce operation
  • array.reduce() method
  • Omitting initial value argument

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How to Use Array Reduce Method in JavaScript
Coy  Roberts

Coy Roberts

1600510680

Definitive Guide to Understand Javascript Array reduce()

Javascript array reduce() is an inbuilt method that is used to apply a function to each element in the array to reduce the array to a single value. The reduce() function executes the provided function for each value of an array from left-to-right. The return value of a function is stored in an accumulator.

Understanding Javascript array reduce()

JavaScript array reduce() is one of the pioneer function of functional programming. The reduce() method accepts two parameters, the total and the current value. If you want to add all the values of an array, then use the array reduce() function.

It is similar to both  Javascript map() and  Javascript filter() but, it differs in the callback arguments.

The callback now receives an accumulator (it accumulates all the return values. Its value is the accumulation of a previously returned accumulations), a current value, a current index, and finally, the whole array.

#javascript #javascript map #javascript filter #javascript array reduce

Terry  Tremblay

Terry Tremblay

1602154740

Fill and Filter in Array in JavaScript

By the word Array methods, I mean the inbuilt array functions, which might be helpful for us in so many ways. So why not just explore and make use of them, to boost our productivity.

Let’s see them together one by one with some amazing examples.

Array.fill():

The _fill()_ method changes all elements in an array to a static value, from a start index (default _0_) to an end index (default _array.length_). It returns the modified array.

In simple words, it’s gonna fill the elements of the array with whatever sets of params, you pass in it. Mostly we pass three params, each param stands with some meaning. The first param value: what value you want to fill, second value: start range of index(inclusive), and third value: end range of index(exclusive). Imagine you are going to apply this method on some date, so that how its gonna look like eg: array.fill(‘Some date’, start date, end date).

NOTE: Start range is inclusive and end range is exclusive.

Let’s understand this in the below example-

//declare array
var testArray = [2,4,6,8,10,12,14];

console.log(testArray.fill("A"));

When you run this code, you gonna see all the elements of testArray will be replaced by 'A' like [“A”,"A","A","A","A","A","A"].

#javascript-tips #array-methods #javascript-development #javascript #arrays

Ollie  Dietrich

Ollie Dietrich

1626424740

JavaScript Array Methods #9: Array .reduce() Method

The JavaScript Array reduce() method executes a reducer function on each element of the array and returns a single output value. Reduce comes with some terminology such as reducer & accumulator. The accumulator is the value that we end with and the reducer is what action we will perform in order to get to one value.

Syntax:
array.reduce(callback(currentvalue, index, arr), thisArg)

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#javascript #reduce #array

Lowa Alice

Lowa Alice

1624388400

JavaScript Arrays Tutorial. DO NOT MISS!!!

Learn JavaScript Arrays

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#arrays #javascript #javascript arrays #javascript arrays tutorial

Madilyn  Kihn

Madilyn Kihn

1590478483

Convert String To Array Using Javascript Split Method

The easiest approach to use javascript built-in method String.split().

#javascript #javascript string #string to array #morioh #array