如何使用JavaScript中的map（）从JavaScript对象提取数据？

Question

我正在尝试使用javascript中的.map()从JSON数据中提取数据。 数据提取需要注入stacked bar chart 。

我正在尝试类似于此问题： 在Chart.js中使用JSON数据堆积条形图，但就我而言，我希望每个赛季的总行驶次数将是barchart的高度，而stacked-barchart的总高度将分为3堆栈。

检查此以获取堆积的条形图： https : //gionkunz.github.io/chartist-js/examples.html#stacked-bar

我的JSON数据：

        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()获得唯一的赛季，然后再次嵌套map()来获得特定锦标赛名称在特定季节的跑步。 我如何解析数据外部json文件。 最终数据应如下所示：

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
]

我想提取数据并将其以3个数组的形式存储在3个数据中：

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

在将数据存储在3个不同的数组中之后，我们可以仅使用解构运算符...来解包数组元素并填充chartdata。

Answer 1

您可以使用Array#reduce创建映射以定义此类过滤对象。

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)

工作代码和邮箱

Answer 2

您可以尝试关注

 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);