javascript - How to cut an array object with a length of 365 into 12 groups by month?

Question

The picture shown is a json file that stores the AQI data for the whole year of 2014. Now I want to calculate the monthly average AQI. How should I process this array?

Answer 1

arr.reduce((r,v)=>r[v.date.split('/')[1]-1].push(v)&&r,new Array(12).fill(0).map(_=>[]))

This return result can return a new array containing 12 arrays, each sub-array contains the AQI data of the current month

I just found out that the main purpose of the poster is to find the average AQI every month, so you can do this:

arr.reduce((r,v)=>r[v.date.split('/')[1]-1].push(v)&&r,new Array(12).fill(0).map(_=>[]))
   .map((i,k)=>{
        let r = i.reduce((r,v)=>{for(let j in r)r[j]+=(+v[j]);return r},{beijing:0,shanghai:0,guangzhou:0});
        for(let j in r) r[j] = parseInt(r[j]/i.length);
        return {...r,month:k+1+'月'}
})    

This result returns an array containing 12 items in the shape of {month:'January',beijing:12,shanghai:24,guangzhou:36}, and the value inside is the average value of each month.

Answer 2

Group by in the background, use avg()

Answer 3

It feels like you don’t need to process the data, which will only continue to consume memory. You only need to know the starting point and ending point of each month, and just use the starting point and ending point to get the array for calculation.
Because in fact, the data It’s all here, it’s just that the rules for how you use the data are different

Answer 4

Your question is mainly about how to divide into 12 groups. I provide two simple ideas

1. Convert date into date object and group by month

2. Use regular rules to get matching dates to group them

Answer 5

From the analysis of the JSON format you gave:

• Peripheral array 1-12, representing 12 months

• Traverse the array again to get object, take the data value of object, divide it according to / to get the month, and fill the object into the corresponding month according to the month

• Get the data corresponding to each month and process it on a monthly basis

Answer 6

Let the back-end process the data grouping, and the front-end is responsible for using it.

Answer 7

var jsonData = [{
    'date': '2014/1/1',
    'beijing': 80,
    'shanghai': 123,
    'guangzhou': 99 
},{
    'date': '2014/1/2',
    'beijing': 80,
    'shanghai': 123,
    'guangzhou': 99 
},{
    'date': '2014/2/1',
    'beijing': 80,
    'shanghai': 123,
    'guangzhou': 99 
}];// 保存的json数据

var arr = [{'date': '1', 'b': 0, 's': 0, 'g': 0}];
var k = 0;
for(var i = 0; i < jsonData.length; i++) {
    var item = jsonData[i];
    var dateArr = item.date.split('/');
    if (dateArr[1] == arr[k].date) {
        arr[k].b += item.beijing;
        arr[k].s += item.shanghai;
        arr[k].g += item.guangzhou;
    } else {
        var param = {
            'date': dateArr[1],
            'b': 0,
            's': 0,
            'g': 0
        };
        k++;
        arr.push(param);
    }
}
console.log(arr);

The above code sums the data of each month. It should be simple to average. However, the above code has a requirement for json data, which is that all the data must be classified according to the month.