如何计算数组中元素的总和和平均值？

Question

Provide detailed answers to this question, including citations and an explanation of why your answer is correct. Answers without enough detail may be edited or deleted.

I am having problems adding all the elements of an array as well as averaging them out. How would I do this and implement it with the code I currently have? The elements are supposed to be defined as I have it below.

<script type="text/javascript">
//<![CDATA[

var i;
var elmt = new Array();

elmt[0] = "0";
elmt[1] = "1";
elmt[2] = "2";
elmt[3] = "3";
elmt[4] = "4";
elmt[5] = "7";
elmt[6] = "8";
elmt[7] = "9";
elmt[8] = "10";
elmt[9] = "11";

// Problem here
for (i = 9; i < 10; i++){
  document.write("The sum of all the elements is: " + /* Problem here */ + " The average of all the elements is: " + /* Problem here */ + "<br/>");
}   

//]]>
</script>

Answer 1

A solution I consider more elegant:

const sum = times.reduce((a, b) => a + b, 0);
const avg = (sum / times.length) || 0;

console.log(`The sum is: ${sum}. The average is: ${avg}.`);

Answer 2

var sum = 0;
for( var i = 0; i < elmt.length; i++ ){
    sum += parseInt( elmt[i], 10 ); //don't forget to add the base
}

var avg = sum/elmt.length;

document.write( "The sum of all the elements is: " + sum + " The average is: " + avg );

Just iterate through the array, since your values are strings, they have to be converted to an integer first. And average is just the sum of values divided by the number of values.

Answer 3

ES6

 const average = arr => arr.reduce( ( p, c ) => p + c, 0 ) / arr.length; const result = average( [ 4, 4, 5, 6, 6 ] ); // 5 console.log(result);

Answer 4

Calculating average (mean) using reduce<\/a> and ES6:

const average = list => list.reduce((prev, curr) => prev + curr) / list.length;

const list = [0, 10, 20, 30]
average(list) // 15

Answer 5

generally average using one-liner reduce is like this

elements.reduce(function(sum, a,i,ar) { sum += a;  return i==ar.length-1?(ar.length==0?0:sum/ar.length):sum},0);

Answer 6

Average Shortest One Liner:<\/strong>

let avg = [1,2,3].reduce((a,v,i)=>(a*i+v)/(i+1));

Answer 7

Let's imagine we have an array of integers like this:

var values = [ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11];

Answer 8

You can also use lodash , _.sum(array) and _.mean(array) in Math part (also have other convenient stuff).

_.sum([4, 2, 8, 6]);
// => 20
_.mean([4, 2, 8, 6]);
// => 5

Answer 9

不是最快的，但最短的一行是使用 map() 和 reduce()：

var average = [7,14,21].map(function(x,i,arr){return x/arr.length}).reduce(function(a,b){return a + b})

Answer 10

I use these methods in my personal library:

Array.prototype.sum = Array.prototype.sum || function() {
  return this.reduce(function(sum, a) { return sum + Number(a) }, 0);
}

Array.prototype.average = Array.prototype.average || function() {
  return this.sum() / (this.length || 1);
}

EDIT: To use them, simply ask the array for its sum or average, like:

[1,2,3].sum() // = 6
[1,2,3].average() // = 2

Answer 11

In ES6-ready<\/strong> browsers this polyfill may be helpful.

Math.sum = (...a) => Array.prototype.reduce.call(a,(a,b) => a+b)

Math.avg = (...a) => this.sum(...a)/a.length;

Answer 12

One sneaky way you could do it although it does require the use of (the much hated) eval().

var sum = eval(elmt.join('+')), avg = sum / elmt.length;
document.write("The sum of all the elements is: " + sum + " The average of all the elements is: " + avg + "<br/>");

Answer 13

Here is a quick addition to the “Math” object in javascript to add a “average” command to it!!

Math.average = function(input) {
  this.output = 0;
  for (this.i = 0; this.i < input.length; this.i++) {
    this.output+=Number(input[this.i]);
  }
  return this.output/input.length;
}

Then i have this addition to the “Math” object for getting the sum!

Math.sum = function(input) {
  this.output = 0;
  for (this.i = 0; this.i < input.length; this.i++) {
    this.output+=Number(input[this.i]);
  }
  return this.output;
}

So then all you do is

alert(Math.sum([5,5,5])); //alerts “15”
alert(Math.average([10,0,5])); //alerts “5”

And where i put the placeholder array just pass in your variable (The input if they are numbers can be a string because of it parsing to a number!)

Answer 14

set your for loop counter to 0.... you're getting element 9 and then you're done as you have it now. The other answers are basic math. Use a variable to store your sum (need to cast the strings to ints), and divide by your array length.

"

Answer 15

Start by defining all of the variables we plan on using. You'll note that for the numbers<\/code> array, I'm using the literal notation of []<\/code> as opposed to the constructor method array()<\/code> . Additionally, I'm using a shorter method to set multiple variables to 0.

var numbers = [], count = sum = avg = 0;

Answer 16

I am just building on Abdennour TOUMI's answer. here are the reasons why:

function getAverage(arry){
    // check if array
    if(!(Object.prototype.toString.call(arry) === '[object Array]')){
        return 0;
    }
    var sum = 0, count = 0; 
    sum = arry.reduce(function(previousValue, currentValue, index, array) {
        if(isFinite(currentValue)){
            count++;
            return previousValue+ parseFloat(currentValue);
        }
        return previousValue;
    }, sum);
    return count ? sum / count : 0; 
};

Answer 17

Array.prototype.avg=function(fn){
    fn =fn || function(e,i){return e};
    return (this.map(fn).reduce(function(a,b){return parseFloat(a)+parseFloat(b)},0) / this.length ) ; 
};

Answer 18

On evergreen browsers you can use arrow functions avg = [1,2,3].reduce((a,b) => (a+b);<\/code>

Answer 19

If you are in need of the average and can skip the requirement of calculating the sum, you can compute the average with a single call of reduce:

// Assumes an array with only values that can be parsed to a Float
var reducer = function(cumulativeAverage, currentValue, currentIndex) {
  // 1. multiply average by currentIndex to find cumulative sum of previous elements
  // 2. add currentValue to get cumulative sum, including current element
  // 3. divide by total number of elements, including current element (zero-based index + 1)
  return (cumulativeAverage * currentIndex + parseFloat(currentValue))/(currentIndex + 1)
}
console.log([1, 2, 3, 4, 5, 6, 7, 8, 9, 10].reduce(reducer, 0)); // => 5.5
console.log([].reduce(reducer, 0)); // => 0
console.log([0].reduce(reducer, 0)); // => 0
console.log([].reduce(reducer, 0)); // => 0
console.log([,,,].reduce(reducer, 0)); // => 0
console.log([].reduce(reducer, 0)); // => 0

Answer 20

If anyone ever needs it - Here is a recursive average.

/**
 * Computes the recursive average of an indefinite set
 * @param {Iterable<number>} set iterable sequence to average
 * @param {number} initAvg initial average value
 * @param {number} initCount initial average count
 */
function average(set, initAvg, initCount) {
  if (!set || !set[Symbol.iterator])
    throw Error("must pass an iterable sequence");

  let avg = initAvg || 0;
  let avgCnt = initCount || 0;
  for (let x of set) {
    avgCnt += 1;
    avg = avg * ((avgCnt - 1) / avgCnt) + x / avgCnt;
  }
  return avg; // or {avg: avg, count: avgCnt};
}

average([2, 4, 6]);    //returns 4
average([4, 6], 2, 1); //returns 4
average([6], 3, 2);    //returns 4
average({
  *[Symbol.iterator]() {
    yield 2; yield 4; yield 6;
  }
});                    //returns 4

Answer 21

Having read the other choices, I will try to make a simpler version for the future viewers, elaborating on the existing code and not creating a more elegant one. First of all, you declared the numbers as strings. Apart from the .parseInt we can also do:

const numberConverter = elmt.map(Number);

So what map does is that it "returns a copy of the original array". But I convert its values to numbers. Then we can use the reduce method (It can also be simpler, but I am writing easy to read versions and I also have 2 average methods) What the reduce method does is it has an accumulator that gets bigger and bigger if you add values to it, as it iterates through the array and adds (in this case) the currentValue to it.:

var i;
const elmt = new Array();
elmt[0] = '0';
elmt[1] = '1';
elmt[2] = '2';
elmt[3] = '3';
elmt[4] = '4';
elmt[5] = '7';
elmt[6] = '8';
elmt[7] = '9';
elmt[8] = '10';
elmt[9] = '11';

console.log(elmt);

const numberConverter = elmt.map(Number);

const sum = numberConverter.reduce((accumulator, currentValue) => {
  return accumulator + currentValue;
}, 0);

const average = numberConverter.reduce(
  (accumulator, currentvalue, index, numArray) => {
    return accumulator + currentvalue / numArray.length;
  },
  0
);

const average2 =
  numberConverter.reduce(
    (accumulator, currentValue) => accumulator + currentValue,
    0
  ) / numberConverter.length;

for (i = 9; i < 10; i++) {
  console.log(
    `The sum of all the elements is: ${sum}. <br> The average of all the elements is: ${average2}`
  );}

Answer 22

I found Mansilla<\/a> 's answer<\/a> to work fine with the extension of making sure that I am doing summation of floats and not concatonation of strings using parseFloat()<\/a> :

let sum = ourarray.reduce((a, b) => parseFloat(a) + parseFloat(b), 0);
let avg = (sum / ourarray.length) || 0;

console.log(sum); // print out sum
console.log(avg); // print out avg

Answer 23

Just for kicks:

var elmt = [0, 1, 2,3, 4, 7, 8, 9, 10, 11], l = elmt.length, i = -1, sum = 0;
for (; ++i < l; sum += elmt[i])
    ;
document.body.appendChild(document.createTextNode('The sum of all the elements is: ' + sum + ' The average of all the elements is: ' + (sum / l)));

Answer 24

I think we can do like

var k=elmt.reduce(function(a,b){return parseFloat(a+parseFloat(b));})
var avg=k/elmt.length; 
console.log(avg);

I am using parseFloat twice because when 1) you add (a)9+b("1") number then result will be "91" but we want addition. so i used parseFloat

2)When addition of (a)9+parseFloat("1") happen though result will be "10" but it will be in string which we don't want so again i used parseFloat.

I hope i am clear. Suggestions are welcome

Answer 25

Here is my rookie way of simply finding the avg. Hope this helps somebody.

function numAvg(num){
    var total = 0;
    for(var i = 0;i < num.length; i++) { 
        total+=num[i];
    }
    return total/num.length;
}

Answer 26

这是你的一个班轮：

var average = arr.reduce((sum,item,index,arr)=>index !== arr.length-1?sum+item:sum+item/arr.length,0)

Answer 27

I think this may be a direct solution to calculate the average with a for loop and function.

var elmts = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11];

function average(arr) {
    var total = 0;
    for (var i = 0; i < arr.length; i++) {
        total += arr[i];
    }
        console.log(Math.round(total/arr.length));
}

average(elmts);

Answer 28

There seem to be an endless number of solutions for this but I found this to be concise and elegant.

const numbers = [1,2,3,4];
const count = numbers.length;
const reducer = (adder, value) => (adder + value);
const average = numbers.map(x => x/count).reduce(reducer);
console.log(average); // 2.5

Answer 29

Unless I missed something, every solution up to this point uses the length of the list to calculate the average after summing the values.

There is a downside to this approach that a slightly modified, yet still simple algorithm will address without the downsides.

The downside is that you assuming that there won't be an overflow by summing all the numbers. If you have a lot of numbers that are very big, and you add them all up, they may exceed the maximum size that can fit into the data type.

A better approach is to simply calculate the average as you go, rather than summing it and then dividing with the length at the end:

function getAvg(values) {
    return values.reduce((m, x, i) => m + (x - m) / (i + 1), 0)
}

Props to Knuth's "Art of Computer Programming" vol. 2.

Answer 30

just for fun

 let avg = [81, 77, -88, 195, 6.8].reduce((a,e,i) => (a*i+e)/(i+1)); console.log(avg)

Answer 31

Average of HTML content itens

With jQuery or Javascript's querySelector you have direct acess to formated data... Example:

<p>Elements for an average: <span class="m">2</span>, <span class="m">4</span>,
   <span class="m">2</span>, <span class="m">3</span>.
</p>

So, with jQuery you have

var A = $('.m')
  .map(function(idx) { return  parseInt($(this).html()) })
  .get();
var AVG = A.reduce(function(a,b){return a+b}) / A5.length;

See other more 4 ways (!) to access itens and average it: http://jsfiddle.net/4fLWB/

Answer 32

var arr = [1,2,3,4,5]

function avg(arr){
  var sum = 0;
  for (var i = 0; i < arr.length; i++) {
    sum += parseFloat(arr[i])
  }
  return sum / i;
}

avg(arr) ======>>>> 3

This works with strings as numbers or numbers in the array.

Answer 33

    var scores =[90, 98, 89, 100, 100, 86, 94];
        var sum = 0;
        var avg = 0;
        for(var i = 0; i < scores.length;i++){
  //Taking sum of all the arraylist
            sum = sum + scores[i];   
                }
  //Taking average     
             avg = sum/scores.length;        
  //this is the function to round a decimal no    
             var round = avg.toFixed();
             console.log(round);

Answer 34

I would recommend D3 in this case. It is the most readable (and provides 2 different kinds of averages)

let d3 = require('d3');
let array = [1,2,3,4];
let sum = d3.sum(array); //10
let mean = d3.mean(array); //2.5
let median = d3.median(array); 

Answer 35

I had exactly 10 elements (like in the example) so I did:

( elmt[0] + elmt[1] + elmt[2] + elmt[3] + elmt[4] +
  elmt[5] + elmt[6] + elmt[7] + elmt[8] + elmt[9] ) / 10