如何使用JavaScript中的map（）從JavaScript對象提取數據？

Question

我正在嘗試使用javascript中的.map()從JSON數據中提取數據。 數據提取需要注入stacked bar chart 。

我正在嘗試類似於此問題： 在Chart.js中使用JSON數據堆積條形圖，但就我而言，我希望每個賽季的總行駛次數將是barchart的高度，而stacked-barchart的總高度將分為3堆棧。

檢查此以獲取堆積的條形圖： https : //gionkunz.github.io/chartist-js/examples.html#stacked-bar

我的JSON數據：

        const batdata=[
    {"season":2008,
     "runs":25,
     "tournamentName":"XYZ"
    },
    {"season":2008,
     "runs":125,
     "tournamentName":"ABC"
    },
    {"season":2008,
     "runs":825,
     "tournamentName":"PQR"
    },
    {"season":2009,
     "runs":425,
     "tournamentName":"XYZ"
    },
    {"season":2009,
     "runs":255,
     "tournamentName":"ABC"
    },
    {"season":2010,
     "runs":275,
     "tournamentName":"XYZ"
    },
    {"season":2010,
     "runs":675,
     "tournamentName":"ABC"
    }
 ];
    export default batdata;

在chart.js中：

import React, { Component } from 'react';
import batdata from './batdata';

const uniq = a => [...new Set(a)]

const uniqueseason = uniq(

  batdata.map( newdata => newdata.season)

)

const runsperseason = batdata.map( newdata => {

})

class Chart extends Component {

  render(){
    return(
      <div>    

      </div>
    )}

}

export default Chart;

我正在使用.map()獲得唯一的賽季，然后再次嵌套map()來獲得特定錦標賽名稱在特定季節的跑步。 我如何解析數據外部json文件。 最終數據應如下所示：

labels  = [2008,2009 2010]

Chartdata = [
    [25, 125, 825]  <--- Height of barchart = 825+25+125 and it will have 3 stacks because there are 3 tournamentName 
    [425, 255, 0]   <-- tournamentName: PQR not present in season 2009 so 3rd element zero
    [275, 675, 0]   <---tournamentName: PQR not present in season 2010 so 3rd element zero
]

我想提取數據並將其以3個數組的形式存儲在3個數據中：

1)Runs in season 2008 for tournamentName: XYZ,ABC, PQR
2)Runs in season 2009 for tournamentName: XYZ, ABC, PQR
3)Runs in season 2010 for tournamentName: XYZ, ABC, PQR

在將數據存儲在3個不同的數組中之后，我們可以僅使用解構運算符...來解包數組元素並填充chartdata。

Answer 1

您可以使用Array#reduce創建映射以定義此類過濾對象。

let filterData = batdata.reduce((filter, value, index) => {

    if (filter[value.season]) {
        filter[value.season] = [...filter[value.season], value.season];
    } else {
        filter[value.season] = [value.season];
    }

    return filter;
}, {});

console.log(filterData)

工作代碼和郵箱

Answer 2

您可以嘗試關注

 const batdata=[{"season":2008,"runs":25,"tournamentName":"XYZ"},{"season":2008,"runs":125,"tournamentName":"ABC"},{"season":2008,"runs":825,"tournamentName":"PQR"},{"season":2009,"runs":425,"tournamentName":"XYZ"},{"season":2009,"runs":255,"tournamentName":"ABC"},{"season":2010,"runs":275,"tournamentName":"XYZ"},{"season":2010,"runs":675,"tournamentName":"ABC"}]; // Create set for unique tournament names let tournaments = new Set(); /* Create an object with key as season name and value as object with ** tournament name as key and run as value */ let obj = batdata.reduce((a,{season, runs, tournamentName}) => { a[season] = a[season] || {}; a[season][[tournamentName]] = runs; tournaments.add(tournamentName); return a; },{}); // Create array from set of unique tournament names tournaments = Array.from(tournaments); // Get the labels - seasons let labels = Object.keys(obj); // Get the data let chartData = Object.values(obj); // Set runs as 0 for missing tournament in the season chartData = chartData.map((o) => tournaments.reduce((a,t) => [...a, o[t] ? o[t] : 0], [])); console.log(labels); console.log(chartData);