targetRow[fieldName] = Number(value);
  console.log(targetRow[fieldName]);                  // => 12
  console.log(targetRow[fieldName]===Number(value));  // => true
  console.log(targetRow);

let execPlanTmp = this.state.execPlan.slice();
execPlanTmp[rowIdx] = targetRow;
this.setState({execPlan: execPlanTmp});
console.log(this.state.execPlan);