no data appears in javascript

I have the following script:

var dataSet;
d3.json("/TableData", function(error, json) {
  if (error) return console.warn(error);
  dataSet = json;
});

$('#data-table').dynatable({
  dataset: {
    records: dataSet
  }
});

/TableData is a sqlalchemy call to a db which returns:

{
  "data": [
{
  "Type": "Turbine", 
  "Seconds": 170, 
}, 
{
  "Type": "Turbine", 
  "Seconds": 75435, 
}]}

I don't get any errors with the console but nothing shows up in the flask website? if I go to http://127.0.0.1/TableData I can see the table data.

This is why because d3.json function is asynchronous and dataSet variable may be set only after the execution of dynatable code.

So try this way.

d3.json("/TableData", function(error, json) {
  if (error) return console.warn(error);
  var dataSet = json;
  $('#data-table').dynatable({
    dataset: {
       records: dataSet
    }
  });
});

You can confirm this by console logging the dataSet variable value from inside the d3.json callback function and outside the function.