Category: JavaScript

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.

Sometimes, we want to count unique elements in array without sorting with JavaScript.

In this article, we’ll look at how to count unique elements in array without sorting with JavaScript.

How to count unique elements in array without sorting with JavaScript?

To count unique elements in array without sorting with JavaScript, we can convert the array to a set and then get its size with the size property.

For instance, we write:

const countUnique = (iterable) => {
  return new Set(iterable).size;
}

console.log(countUnique([5, 6, 5, 6]));

We create the countUniquer function that takes an iterable object.

In the function, we convert iterable to a set with the Set constructor.

And then we get the size of the set with the size property.

Therefore, the console log should log 2.

Conclusion

To count unique elements in array without sorting with JavaScript, we can convert the array to a set and then get its size with the size property.

Sometimes, we want to set a new ID for a element with jQuery.

In this article, we’ll look at how to set a new ID for a element with jQuery.

How to set a new ID for a element with jQuery?

To set a new ID for a element with jQuery, we can call the attr method.

For instance, we write:

<div>
  hello world
</div>

to add a div.

Then we write:

$('div').attr('id', 'foo')

to select the div with $.

Then we call attr with the attribute name and value respectively.

Therefore, the div should now have the id attribute set to foo.

Conclusion

To set a new ID for a element with jQuery, we can call the attr method.