Can this function be done with Array.prototype method

Question

I'm trying to adopt the new Array.prototype functions, and wondering how is this code can be done with it.

The goal is, return the average value of every 12 object as an array from the original object array.

var WeatherData = [{tm:0,t:22,h:15,p:537}..
var AverageWeather = []; 
var temp = 0;

for (i = 0; i < WeatherData.length; i++) {

    temp += WeatherData[i].t;
    if ((i+1) % 12 == 0) {
    AverageWeather.push( Math.round((temp / 12) * 100) / 100 );
    Temp = 0;
    }
}

console.log(AverageWeather);

fiddle: https://jsfiddle.net/xd2v62rL/

Answer 1

This becomes easier to solve using the the Array.prototype methods map reduce etc when you split the data into groups of 12 before you attempt to calculate the averages:

var weatherData = [{tm:0,t:22,h:15,p:537},{tm:5,t:13,h:42,p:895},{tm:10,t:21,h:36,p:582},{tm:15,t:22,h:51,p:986},{tm:20,t:21,h:36,p:902},{tm:25,t:22,h:58,p:439},{tm:30,t:16,h:57,p:1042},{tm:35,t:20,h:14,p:480},{tm:40,t:20,h:34,p:958},{tm:45,t:17,h:7,p:403},{tm:50,t:13,h:69,p:460},{tm:55,t:20,h:36,p:967},{tm:60,t:19,h:57,p:419},{tm:65,t:18,h:43,p:746},{tm:70,t:17,h:49,p:344},{tm:75,t:16,h:90,p:651},{tm:80,t:19,h:96,p:646},{tm:85,t:19,h:3,p:301},{tm:90,t:14,h:96,p:770},{tm:95,t:17,h:54,p:1036},{tm:100,t:15,h:79,p:890},{tm:105,t:22,h:32,p:1041},{tm:110,t:22,h:67,p:415},{tm:115,t:20,h:82,p:616}];

var groups = [];

while(weatherData.length) {
    groups.push(weatherData.splice(0, 12));
}

var averageWeather = groups.map(function(g) {
    return Math.round((g.reduce(function(acc, val) { 
       return acc + val.t
    }, 0) / 12) * 100) / 100;
});

console.log(averageWeather);

Answer 2

Array.prototype.getAverageWeather = function() {
    var AverageWeather = []; 
    var temp = 0;

    for (i = 0; i < this.length; i++) {

        temp += this[i].t;
        if ((i+1) % 12 == 0) {
      AverageWeather.push( Math.round((temp / 12) * 100) / 100 );
        Temp = 0;
        }
    }

    return AverageWeather;
}

var WeatherData = [{tm:0,t:22,h:15,p:537},{tm:5,t:13,h:42,p:895},{tm:10,t:21,h:36,p:582},{tm:15,t:22,h:51,p:986},{tm:20,t:21,h:36,p:902},{tm:25,t:22,h:58,p:439},{tm:30,t:16,h:57,p:1042},{tm:35,t:20,h:14,p:480},{tm:40,t:20,h:34,p:958},{tm:45,t:17,h:7,p:403},{tm:50,t:13,h:69,p:460},{tm:55,t:20,h:36,p:967},{tm:60,t:19,h:57,p:419},{tm:65,t:18,h:43,p:746},{tm:70,t:17,h:49,p:344},{tm:75,t:16,h:90,p:651},{tm:80,t:19,h:96,p:646},{tm:85,t:19,h:3,p:301},{tm:90,t:14,h:96,p:770},{tm:95,t:17,h:54,p:1036},{tm:100,t:15,h:79,p:890},{tm:105,t:22,h:32,p:1041},{tm:110,t:22,h:67,p:415},{tm:115,t:20,h:82,p:616}];

console.log(WeatherData.getAverageWeather());

This way you can attach the function to Array prototype.

Answer 3

You can combination of reduce and map for this

 let averages = WeatherData
 .reduce(groupInto12, [])
 .map(getAverage);

function groupInto12(rows, key, index){
    if(index % 12 === 0)
       rows.push([key])
    else
       rows[rows.length-1].push(key)
       return rows;
}
function getAverage (tempfor12days) {
  let totalTemp = tempfor12days.reduce((acc,val)=>acc+val.t,0);
  return Math.round((totalTemp / 12) * 100) / 100;
 }