Using javascript to download file as a.csv file

Question

Hi I am trying to export a file as .csv file, so that when the user clicks on the download button, the browser would automatically download the file as .csv. I also want to

Answer 1

If your data comes from a SQL Database, all your lines should have the same structure, but if coming from a NoSQL Database you could have trouble using standard answers. I elaborated on above JSON2CSV for such a scenario. Json data example

  [ {"meal":2387,"food":"beaf"},
    {"meal":2387,"food":"apple","peeled":"yes", "speed":"fast" },
    {"meal":2387,"food":"pear", "speed":"slow", "peeled":"yes" } ]

Answer

"meal","food","peeled","speed"
"2387","beaf","",""
"2387","apple","yes","fast"
"2387","pear","yes","slow"

Code for headers and double quotes for simplicity.

function JSON2CSV(objArray) {
  var array = typeof objArray != 'object' ? JSON.parse(objArray) : objArray;

  var str = '';
  var line = '';

  // get all distinct keys      
  let titles = [];
  for (var i = 0; i < array.length; i++) {
    let obj = array[i];
    Object.entries(obj).forEach(([key,value])=>{
      //console.log('key=', key, "   val=", value );
      if (titles.includes(key) ) {
        // console.log (key , 'exists');
        null;
      }
      else {
        titles.push(key);
      }
    })
  }
  let htext =  '"' + titles.join('","') + '"';
  console.log('header:', htext);
  // add to str
  str += htext + '\r\n';
  //
  // lines
  for (var i = 0; i < array.length; i++) {
    var line = '';
    // get values by header order
    for (var j = 0; j < titles.length; j++) {
      // match keys with current header
      let obj = array[i];
      let keyfound = 0;    
      // each key/value pair
      Object.entries(obj).forEach(([key,value])=>{
        if (key == titles[j]) {
          // console.log('equal tit=', titles[j] , ' e key ', key ); // matched key with header
          line += ',"' + value +  '"';
          keyfound = 1; 
          return false;
        }

      })
      if (keyfound == 0) {
        line += ',"'  +  '"';   // add null value for this key
      } // end loop of header values

    }

    str += line.slice(1) + '\r\n';
  }
  return str;
}