Category: JavaScript Answers

Sometimes, we want to detect support for VML or SVG in a browser with JavaScript.

In this article, we’ll look at how to detect support for VML or SVG in a browser with JavaScript.

How to detect support for VML or SVG in a browser with JavaScript?

To detect support for VML or SVG in a browser with JavaScript, we can use the document.implementation.hasFeature method.

For instance, we write:

document.implementation.hasFeature("http://www.w3.org/TR/SVG11/feature#Shape", "1.0")

to detect SVG support in the browser.

If it returns true, then it’s supported.

Conclusion

To detect support for VML or SVG in a browser with JavaScript, we can use the document.implementation.hasFeature method.

Sometimes, we want to paginate a JavaScript array.

In this article, we’ll look at how to paginate a JavaScript array.

How to paginate a JavaScript array?

To paginate a JavaScript array, we can use the JavaScript array’s slice method.

For instance, we write:

const paginate = (array, pageSize, pageNumber) => {
  return array.slice((pageNumber - 1) * pageSize, pageNumber * pageSize);
}

console.log(paginate([1, 2, 3, 4, 5, 6], 2, 2));
console.log(paginate([1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11], 4, 1));

to create the paginate function that takes the array we want to pagination and the pageSize and pageNumber.

In the function, we call array.slice to return the elements that should be in the given pageNumber given the pageSize.

We pass in (pageNumber - 1) * pageSize as the start index and pageNumber * pageSize as the end index.

Therefore, from the console log, we get [3, 4] and [1, 2, 3, 4] respectively.

Conclusion

To paginate a JavaScript array, we can use the JavaScript array’s slice method.

Sometimes, we want to output text based on user’s current time with JavaScript.

In this article, we’ll look at how to output text based on user’s current time with JavaScript.

How to output text based on user’s current time with JavaScript?

To output text based on user’s current time with JavaScript, we can use the JavaScript date’s getHours method to get the hour of the day.

Then we can use an if statement to output text according to the hour of the day.

For instance, we write:

const today = new Date()
const curHr = today.getHours()

if (curHr < 12) {
  console.log('good morning')
} else if (curHr < 18) {
  console.log('good afternoon')
} else {
  console.log('good evening')
}

We get the current date and time with new Date().

Then we get the hour of the current date and time with getHours.

Finally, we use an if-else statement to check for the hour.

If it’s less than 12, then it’s morning.

If it’s less than 18, then it’s afternoon.

Otherwise, it’s evening.

Conclusion

To output text based on user’s current time with JavaScript, we can use the JavaScript date’s getHours method to get the hour of the day.

Then we can use an if statement to output text according to the hour of the day.

Sometimes, we want to listen to click events on a bar chart with Chart.js.

In this article, we’ll look at how to listen to click events on a chart with Chart.js.

How to listen to click events on a chart with Chart.js?

To listen to click events on a bar chart with Chart.js, we set the options.onClick property to an event handler function.

For instance, we write:

<script src="https://cdnjs.cloudflare.com/ajax/libs/Chart.js/3.5.1/chart.min.js"></script>

<canvas id='myChart' style='width: 300px; height: 300px'></canvas>

to add the canvas for the chart.

Then we write:

const ctx = document.getElementById('myChart').getContext('2d');
const myChart = new Chart(ctx, {
  type: 'line',
  data: {
    labels: ['Monday', 'Tuesday', 'Wednesday'],
    datasets: [{
      label: '# of Votes',
      data: [12, 19, 3],
      borderWidth: 1,
      borderColor: 'green'
    }]
  },
  options: {
    onClick(e) {
      console.log(e)
    }
  }
});

to set the options.onClick property to the click event listener.

Now when we click on an item in the chart, we should see the click event object logged.

Conclusion

To listen to click events on a bar chart with Chart.js, we set the options.onClick property to an event handler function.