Share the method of summing and maximizing JS arrays

Preface

An issue encountered in the interview: the JS array sum function. The first thing I think of is array loops. However, I think the interviewer asked this question not to take the well-known method. At that time, I was so clever that I thought of the recursive function constantly adding items to the array, but I couldn't adjust the method after a long time. It turned out that this was not the optimal solution. Finally, the interviewer asked me if I had seen itreduce(), there is no such thing as it is. So come back to check the information,()It is a new attribute added to ES5, and similar ones are also()。

Let’s summarize the method of summing arrays below.

The roughest way: loop acquisition

Add one by one through the for loop. Look at the code:

 = function (){
 var result = 0;
 for(var i = 0; i < ; i++) {
  result += this[i];
 }
 return result;
};

[1,4,7,2,10].sum(); // 24

Use reduce method

usereduceMethod, you can write an array sumsummethod.

reduce()The method receives a function as an accumulator, and each value in the array (from left to right) begins to shrink and ends up being a value.

Syntax of reduce:

(callback[, initialValue]);

callbackThe function accepts 4 parameters:previousValue(The value returned by the last callback)currentValue(The element currently being processed),index(index) and the array itself (first callcallbackThe first parameter of ) executes the function for each value in the array.

initialValueThe parameters are optional, representing the initial value;initialValueIf specified, the parameter is deemed to be used initially.previousValue, if default, use the first element of the array aspreviousInitial value, at the same timecurrentOne in the back row.

 = function (){
 return (function (partial, value){
  return partial + value;
 })
};
[1,4,7,2,10].sum(); // 24

Compared with the first method,reduce()The method is more efficient.

The efficiency comparison of these two methods can be called directly before and after the function is run.new Date()Get instant time, thereby comparing execution time by time difference. I won’t compare it here because everyone’s execution environment varies greatly. The test results arereduce()The execution time of the method is shorter.

JS array sum function and find the maximum value in the array

Example code

&lt;!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http:///TR/xhtml1/DTD/"&gt;

&lt;html xmlns="http:///1999/xhtml"&gt;

&lt;head&gt;

&lt;meta http-equiv="Content-Type" content="text/html; charset=gb2312" /&gt;

&lt;title&gt;I_jsArray sum and maximum method_I网&lt;/title&gt;

&lt;meta name="keywords" content="Webmaster, web page special effects, web page special effects code, js special effects, js script, script, advertising code,,, my website" /&gt;

&lt;meta name="description" content=",My website, webmasters must have js special effects and advertising codes. A large number of high-quality js special effects, providing high-quality advertising code downloads, all on my website" /&gt;

&lt;/head&gt;

&lt;body&gt;

&lt;a href="https:///">My website</a>, the webmaster must have high-quality web page special effects and advertising code., webmaster js special effects. <hr>
&lt;script type="text/javascript"&gt;

//Sum
 = function () {

 for (var sum = i = 0; i &lt; ; i++)sum += parseInt(this[i]);

  return sum ;

};

// Find the maximum value
 = function () {

 for (var i = 0, maxValue = Number.MIN_VALUE; i &lt; ; i++)parseInt(this[i]) &gt; maxValue &amp;&amp; (maxValue = this[i]);

 return maxValue;

};

//application
var arr = [1,21,3,4,22,45,60,7,32];

alert(("+") + "=" + ()); alert(("|") + "The largest number is:" + ());

&lt;/script&gt;

&lt;/body&gt;

&lt;/html&gt;

The above is all the content of this article. I hope it will be helpful to everyone using JavaScript. If you have any questions, please leave a message and discuss it. The editor will reply to everyone in time.