Chart.js x-axis date label is not in order

Chart.js x-axis date label is not in order

If you are using Chart.js to create charts with date labels on the x-axis, you may have encountered a common issue where the date labels are not displayed in the correct order. This can be frustrating, especially when you are trying to visualize time-based data accurately. In this blog post, we will explore a couple of solutions to this problem.

Solution 1: Sorting the data array

One way to ensure that the date labels are displayed in the correct order is to sort the data array before passing it to Chart.js. This can be done by using the sort method with a custom comparison function that compares the date values.

const data = [
  { date: '2022-01-01', value: 10 },
  { date: '2022-01-03', value: 20 },
  { date: '2022-01-02', value: 15 },
];

data.sort((a, b) => new Date(a.date) - new Date(b.date));

// Use the sorted data array to create the chart
new Chart(ctx, {
  type: 'line',
  data: {
    labels: data.map(item => item.date),
    datasets: [{
      label: 'Value',
      data: data.map(item => item.value),
    }],
  },
  options: {
    // Chart options
  },
});

This solution sorts the data array based on the date values using the sort method and a custom comparison function. The sorted data array is then used to create the chart, ensuring that the date labels are displayed in the correct order.

Solution 2: Using a time-based x-axis

Another solution is to use a time-based x-axis instead of using string labels for the dates. Chart.js provides a built-in time scale that can be used to handle time-based data more effectively.

// Use the moment.js library to parse and format dates
const data = [
  { date: '2022-01-01', value: 10 },
  { date: '2022-01-03', value: 20 },
  { date: '2022-01-02', value: 15 },
];

// Use the moment.js library to parse and format dates
const formattedData = data.map(item => ({
  x: moment(item.date),
  y: item.value,
}));

// Use the time scale for the x-axis
new Chart(ctx, {
  type: 'line',
  data: {
    datasets: [{
      label: 'Value',
      data: formattedData,
    }],
  },
  options: {
    scales: {
      x: {
        type: 'time',
        time: {
          unit: 'day',
        },
      },
    },
  },
});

In this solution, we use the moment.js library to parse and format the dates. The data array is transformed into a new array where each date is represented by a moment.js object. The time scale is then used for the x-axis, with the unit set to ‘day’. This ensures that the date labels are displayed in the correct order.

By implementing one of these solutions, you can ensure that the x-axis date labels in your Chart.js charts are displayed in the correct order, allowing you to visualize time-based data accurately.

Do you have any other questions or issues with TypeScript and Chart.js? Let us know in the comments below!

Final HTML Output:

<

pre>

const data = [
  { date: '2022-01-01', value: 10 },
  { date: '2022-01-03', value: 20 },
  { date: '2022-01-02', value: 15 },
];

data.sort((a, b) => new Date(a.date) - new Date(b.date));

// Use the sorted data array to create the chart
new Chart(ctx, {
  type: 'line',
  data: {
    labels: data.map(item => item.date),
    datasets: [{
      label: 'Value',
      data: data.map(item => item.value),
    }],
  },
  options: {
    // Chart options
  },
});