JS - Download CSV from JSON

JS - Download CSV from JSON
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Single Array of JSON compose in CSV file

html
-------
<div Onclick="downloadCSV()"> CSV Format Download </div>

API.json
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"sections": {
"table1": [{
          "table1column1": "t1c1",
          "table1coloumn2": "t1c2"
          },
          {
          "table1column1": "t12c1",
          "table1coloumn2": "t12c2"
          }]
}

<script>
var jsonData = data.section.table1; // compose  csv data

var keys = ['table1column1','table1coloumn2'];
var header = ['Table1 Column1', 'Table1 column2']


downloadCSV(){

let filteredData = this.getCSV(keys,jsonData);
    let ReportTitle = filename+ " " +level+" "+id;
    let ShowLabel = true;
    var arrData = typeof filteredData != 'object' ? JSON.parse(filteredData) : filteredData;
    var CSV = '';
    if (ShowLabel) {
      var row = "";
 
 //CSV column header is composing here and assamble in row1,column1
      for (let index=0;index<header.length;index++) {
        row += header[index] + ',';
      }
      row = row.slice(0, -1);
      CSV += row + '\r\n';
    }
    for (var i = 0; i < arrData.length; i++) {
      var row = "";
      for (var index in arrData[i]) {
        row += '"' + arrData[i][index] + '",';
      }
      row.slice(0, row.length - 1);
      CSV += row + '\r\n';
    }

    if (CSV == '') {
      console.log("Invalid data");
      return;
    }
    var fileName = ReportTitle.replace(/ /g, "_");
    var uri = 'data:text/csv;charset=utf-8,' + encodeURI(CSV);
    var link = document.createElement("a");
    link.href = uri;
    link.download = fileName + ".csv";
    document.body.appendChild(link);
    link.click();
    document.body.removeChild(link);

}

getCSV(keys,jsonObj){

let k=[];
     for(let i=0;i<jsonObj.length;i++){
         let item = {};
         for(let m=0;m<keys.length;m++){
         item[keys[m]]=jsonObj[i][keys[m]];
         }
        k.push(item);
       }      
       return k;

}