for (var i = 0; i < field.length; i++) {
       dataPointsA.push( "['" + field[i].time + "','" + field[i].xxx + "']" );
       dataPointsB.push( "['" + field[i].time + "','" + field[i].yyy +  "']" );
}

console.log(dataPointsA);
console.log(dataPointsB);

data: [[ '2019-04-30','0' ], [ '2019-05-01','0' ], [ '2019-05-09','3' ], [ '2019-05-21','0' ], [ '2019-05-24','0' ]]