Preface
I encountered a problem during the interview: JS array sum function. The first thing that comes to my mind is array looping. However, I feel that when the interviewer asks this question, he must not be trying to test this well-known method. At that time, I was smart enough to think of a recursive function that continuously adds the items of the array. However, after struggling for a long time, I couldn't adjust the method. It turns out that this is not the optimal solution. Finally, the interviewer asked me if I had ever seen reduce(), and I really didn’t. So I came back to check the information. Array.reduce() is a new attribute added by ES5, and Array.reduceRight() is similar.
The following is a summary of the array summation method.
The crudest method: Loop to obtain
Add item by item through a for loop. Look at the code:
Array.prototype.sum = function (){
var result = 0;
for(var i = 0; i < this.length; i++) {
result += this[i];
}
return result;
};
[1,4,7,2,10].sum(); // 24
Use the reduce method
Using the reduce method, you can write a sum method for array summation.
The reduce() method receives a function as an accumulator. Each value in the array (from left to right) starts to be reduced, and finally becomes a value.
Reduce syntax:
array.reduce(callback[, initialValue]);
The callback function accepts 4 parameters: previousValue (the value returned by the last callback call), currentValue (the element currently being processed), index (index) and the array itself (the first parameter of the first callback call), execute the function for each value in the array.
The initialValue parameter is optional and represents the initial value; if the initialValue parameter is specified, it will be regarded as the previous value initially used. If it is defaulted, the first element of the array will be used as the initial value of previous, and current will follow. Rank one.
Array.prototype.sum = function (){
return this.reduce(function (partial, value){
return partial + value;
})
};
[1,4,7,2,10].sum(); // 24
Compared with the first method, using the reduce() method is more efficient.
To compare the efficiency of these two methods, you can directly call new Date() before and after the function is run to obtain the real-time time, so as to compare the execution time through the time difference. There will be no comparison here, because everyone's execution environment is quite different. The test result is that the execution time of the reduce() method is shorter.
JS array sum function and find the maximum value in the array
Example code
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=gb2312" />
<title>php中文网_js数组求和和最大值方法_php中文网</title>
<meta name="keywords" content="站长,网页特效,网页特效代码,js特效,js脚本,脚本,广告代码,php.cn,www.php.cn,php中文网" />
<meta name="description" content="www.php.cn,php中文网，站长必备js特效及广告代码。大量高质量js特效，提供高质量广告代码下载,尽在php中文网" />
</head>
<body>
<a href="http://www.php.cn/">php中文网<</a>,站长必备的高质量网页特效和广告代码。jb51.net，站长js特效。<hr>
<script type="text/javascript">
//求和
Array.prototype.sum = function () {
for (var sum = i = 0; i < this.length; i++)sum += parseInt(this[i]);
return sum ;
};
//求最大值
Array.prototype.maxima = function () {
for (var i = 0, maxValue = Number.MIN_VALUE; i < this.length; i++)parseInt(this[i]) > maxValue && (maxValue = this[i]);
return maxValue;
};
//应用
var arr = [1,21,3,4,22,45,60,7,32];
alert(arr.join("+") + "=" + arr.sum()); alert(arr.join("|") + "中, 最大的数是:" + arr.maxima());
</script>
</body>
</html>
The above is the entire content of this article , I hope it will be helpful to everyone in using JavaScript. If you have any questions, please leave a message for discussion. The editor will reply to you in time.
For more articles sharing methods of summing and maximizing JS arrays, please pay attention to the PHP Chinese website!
Replace String Characters in JavaScriptMar 11, 2025 am 12:07 AMDetailed explanation of JavaScript string replacement method and FAQ This article will explore two ways to replace string characters in JavaScript: internal JavaScript code and internal HTML for web pages. Replace string inside JavaScript code The most direct way is to use the replace() method: str = str.replace("find","replace"); This method replaces only the first match. To replace all matches, use a regular expression and add the global flag g: str = str.replace(/fi
Custom Google Search API Setup TutorialMar 04, 2025 am 01:06 AMThis tutorial shows you how to integrate a custom Google Search API into your blog or website, offering a more refined search experience than standard WordPress theme search functions. It's surprisingly easy! You'll be able to restrict searches to y
8 Stunning jQuery Page Layout PluginsMar 06, 2025 am 12:48 AMLeverage jQuery for Effortless Web Page Layouts: 8 Essential Plugins jQuery simplifies web page layout significantly. This article highlights eight powerful jQuery plugins that streamline the process, particularly useful for manual website creation
Build Your Own AJAX Web ApplicationsMar 09, 2025 am 12:11 AMSo here you are, ready to learn all about this thing called AJAX. But, what exactly is it? The term AJAX refers to a loose grouping of technologies that are used to create dynamic, interactive web content. The term AJAX, originally coined by Jesse J
What is 'this' in JavaScript?Mar 04, 2025 am 01:15 AMCore points This in JavaScript usually refers to an object that "owns" the method, but it depends on how the function is called. When there is no current object, this refers to the global object. In a web browser, it is represented by window. When calling a function, this maintains the global object; but when calling an object constructor or any of its methods, this refers to an instance of the object. You can change the context of this using methods such as call(), apply(), and bind(). These methods call the function using the given this value and parameters. JavaScript is an excellent programming language. A few years ago, this sentence was
10 Mobile Cheat Sheets for Mobile DevelopmentMar 05, 2025 am 12:43 AMThis post compiles helpful cheat sheets, reference guides, quick recipes, and code snippets for Android, Blackberry, and iPhone app development. No developer should be without them! Touch Gesture Reference Guide (PDF) A valuable resource for desig
Improve Your jQuery Knowledge with the Source ViewerMar 05, 2025 am 12:54 AMjQuery is a great JavaScript framework. However, as with any library, sometimes it’s necessary to get under the hood to discover what’s going on. Perhaps it’s because you’re tracing a bug or are just curious about how jQuery achieves a particular UI
How do I create and publish my own JavaScript libraries?Mar 18, 2025 pm 03:12 PMArticle discusses creating, publishing, and maintaining JavaScript libraries, focusing on planning, development, testing, documentation, and promotion strategies.
Hot AI Tools
Undresser.AI Undress
AI-powered app for creating realistic nude photos
AI Clothes Remover
Online AI tool for removing clothes from photos.
Undress AI Tool
Undress images for free
Clothoff.io
AI clothes remover
AI Hentai Generator
Generate AI Hentai for free.
Hot Article
Hot Tools
Dreamweaver Mac version
Visual web development tools
VSCode Windows 64-bit Download
A free and powerful IDE editor launched by Microsoft
MinGW - Minimalist GNU for Windows
This project is in the process of being migrated to osdn.net/projects/mingw, you can continue to follow us there. MinGW: A native Windows port of the GNU Compiler Collection (GCC), freely distributable import libraries and header files for building native Windows applications; includes extensions to the MSVC runtime to support C99 functionality. All MinGW software can run on 64-bit Windows platforms.
PhpStorm Mac version
The latest (2018.2.1) professional PHP integrated development tool
SAP NetWeaver Server Adapter for Eclipse
Integrate Eclipse with SAP NetWeaver application server.
