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Editor to share with you how to achieve js Array.prototype.reduce method, I believe that most people do not know much about it, so share this article for your reference, I hope you will learn a lot after reading this article, let's go to understand it!

Manually implement the Array.prototype.reduce method

The reduce () method executes a reducer function (in ascending order) provided by you on each element in the array, summarizing its results into a single return value.

Function reduce (arr, reduceCallback, initialValue) {/ / first, check whether the passed parameters are correct. If (! Array.isArray (arr) | |! arr.length | | typeof reduceCallback! = = 'function') {return [];} else {/ / if initialValue is not passed to this function, we will use the first array item as initialValue let hasInitialValue = initialValue! = = undefined; let value = hasInitialValue? InitialValue: arr [0];, / / if initialValue is passed, the index starts from 1, otherwise for starts from 0 (let I = hasInitialValue? 1: 0, len = arr.length; I < len; iTunes +) {value = reduceCallback (value, arr [I], I, arr);} return value;}} these are all the contents of the article "how js implements the Array.prototype.reduce method". Thank you for reading! I believe we all have a certain understanding, hope to share the content to help you, if you want to learn more knowledge, welcome to follow the industry information channel!

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