Dynamic Chart with JSON data - CanvasJS

Question

I have an issue generating a chart with CanvasJS.

Basically I get the data from the API, I can see and check the JSON array but when I'm going to generate the dataPoint for the graph I get 2 errors: data invalid on the data field and NaN on the value field.

Can someone give me a hint?

// Fetching the data
fetch('https://example.com/my/endpoint').then(response => {
  return response.json();
}).then(data => {
  // Work with JSON data here
 var jsonData = data;
 // Generating Data Points
 var dataPoints = [];
 
for (var i = 0; i <= jsonData.length - 1; i++) {
    dataPoints.push({ y: new Date(jsonData[i].source_ts), x: Number(jsonData[i].xyzw) });
    console.log(dataPoints);
}

var chart = new CanvasJS.Chart("chartContainer", {
    data: [
        {
            dataPoints: dataPoints,
            type: "line",
        }
    ]
});

chart.render();
}).catch(err => {
 throw new Error( 'Impossible to get data' );
});

Cheers

score 2 · Accepted Answer · answered Aug 30 '18 at 07:43

You were not intreating correctly over data due to which you were getting y:null and x:NaN.

Content inside data is array of objects inside an array i.e. [[{}, {}, {}...]]so you need to iterate accordingly.

Use this code:

  data.forEach(function(array) {
    array.forEach(function(arrayItem) {
      dataPoints.push({
        y: new Date(arrayItem.source_ts),
        x: Number(arrayItem.renewablesobligationconsumption)
      });
    });
  });

Below is complete working example. Now your dataPoints is ready, you can use it anywhere you want:

// Fetching the data
fetch('https://example.com/my/endpoint').then(response => {
  return response.json();
}).then(data => {

  // Generating Data Points
  var dataPoints = [];

  data.forEach(function(array) {
    array.forEach(function(arrayItem) {
      dataPoints.push({
        y: new Date(arrayItem.source_ts),
        x: Number(arrayItem.xyzw)
      });
    });
  });
  
 console.log(dataPoints);

  var chart = new CanvasJS.Chart("chartContainer", {
    data: [{
      dataPoints: dataPoints,
      type: "line",
    }]
  });

  chart.render();
}).catch(err => {
  throw new Error('Impossible to get data');
});

<br/>
<!-- Just so that JSFiddle's Result label doesn't overlap the Chart -->

<div id="chartContainer" style="height: 300px; width: 100%;"></div>

Downvoter please mention the reason of downvoting an already accepted answer. Thank you — Vikasdeep Singh, Aug 30 '18 at 12:27

Dynamic Chart with JSON data - CanvasJS

1 Answers1