How to use reduce function in JavaScript

This article will explain in detail how to use the reduce function in JavaScript. The editor thinks it is very practical, so I share it for you as a reference. I hope you can get something after reading this article.

Reduce function

Syntax: arr.reduce (callback (accumulator, currentValue [, index [, array]]) [, initialValue])

Method function: execute a reducer function (in ascending order) provided by you on each element in the array and summarize the results into a single return value.

Return: the result of the cumulative processing of the function.

Custom function: myReduce.

Array.prototype.myReduce = function (callbackFn, initialValue) {if (typeof callbackFn! = = 'function') throw (' callbackFn parameter must be a function'); let element = this, len = element.length | | 0, index = 0, result; if (arguments.length > = 2) {result = arguments [1];} else {while (index)

< len && !(index in element)) index++; if (index >

= len) throw new TypeError ('Reduce of empty array' + 'with no initial value'); result = element [index++];} while (index < len) {if (index in element) result = callbackFn (result, element [index], index, element); index++;} return result } this is the end of the article on "how to use the reduce function in JavaScript". I hope the above content can be of some help to you, so that you can learn more knowledge. if you think the article is good, please share it for more people to see.