Category: JavaScript Answers

Categories
Chart.js JavaScript Answers

How to disable everything on hover with Chart.js?

selective focus photography of white dog

Sometimes, we want to disable everything on hover with Chart.js.

In this article, we’ll look at how to disable everything on hover with Chart.js.

How to disable everything on hover with Chart.js?

To disable everything on hover with Chart.js, we can set the options.events property to an empty array.

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 Chart.js script and canvas.

And 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: {
    events: []
  }
});

to select the canvas and add a line chart into it.

We set options.events to an empty array to disable everything on hover.

Now when we hover over the graph, we shouldn’t see any tooltips or hover effects displayed.

Conclusion

To disable everything on hover with Chart.js, we can set the options.events property to an empty array.

Categories
JavaScript Answers jQuery

How to show a “are you sure?” dialog when we click on a link with JavaScript or jQuery?

white and brown long coated small dog

Sometimes, we want to show a "are you sure?" dialog when we click on a link with JavaScript or jQuery.

In this article, we’ll look at to show a "are you sure?" dialog when we click on a link with JavaScript or jQuery.

How to show a "are you sure?" dialog when we click on a link with JavaScript or jQuery?

To show a "are you sure?" dialog when we click on a link with JavaScript or jQuery, we can call the confirm function in the click event handler of a link.

For instance, we write:

<a href="/DoSomethingDangerous" class='confirm'>do something dangerous</a>

to add the link.

Then we write:

$(() => {
  $('.confirm').click((e) => {
    return window.confirm("Are you sure?");
  });
});

We select the link with $.

And we call click with the click event handler for the link.

In the click event handler, we call window.confirm with the text we want to show in the dialog.

Now when we click on the link, we see ‘Are you sure?’ displayed.

And we can click OK or Cancel to dismiss it.

Conclusion

To show a "are you sure?" dialog when we click on a link with JavaScript or jQuery, we can call the confirm function in the click event handler of a link.

Categories
JavaScript Answers Nodejs

How to read a CSV text file with Node.js?

(Source code is at https://github.com/jauyeunggithub/rook-hotel-answers/blob/master/q3.txt)

Sometimes, we want to read a CSV text file with Node.js.

In this article, we’ll look at how to read a CSV text file with Node.js.

How to read a CSV text file with Node.js?

To read a CSV text file with Node.js, we can use the fs.readFile method.

For instance, if we have:

foo.txt

id,name,value
1,James,50
2,Pete,300
3,Jane,400
4,Alex,200

Then we write:

const fs = require('fs')
fs.readFile('./foo.txt', (err, file) => {
  const rows = file.toString().trim().split('\n')
  let total = 0
  for (const r of rows) {
    const [, , val] = r.split(',')
    if (!isNaN(+val)) {
      total += +val
    }
  }
  console.log(total)
})

to import the fs module with require.

Then we call readFile with the file path and a callback to get the file content from the file parameter.

We call file.toString to convert the contents to a string.

Then we call trim and split to trim and split the string by the new line character.

Next, we define total and loop through rows to get the value of the number column and assign to val with destructuring.

Then we check if val is a number with isNaN and negation.

If it is, then we add it to total.

Therefore, we see total is 950 from the console log.

Conclusion

To read a CSV text file with Node.js, we can use the fs.readFile method.

Categories
JavaScript Answers

How to use modulo operator (%) in JavaScript?

white and brown long coated small dog

(Source code is at https://github.com/jauyeunggithub/rook-hotel-answers/blob/master/q2.txt)

The modulo operator (%) in JavaScript lets us get the remainder when we divide one number by the other.

In this article, we’ll look at how to use modulo operator (%) in JavaScript.

How to use modulo operator (%) in JavaScript?

We can use the modulo operator to get the remainder of the left operand divided by the right one.

For instance, we write:

const numFn = (num) => {
  if (num % 14 === 0) {
    console.log('foobar')
    return
  } else if (num % 7 === 0) {
    console.log('foo')
    return
  } else if (num % 2 === 0) {
    console.log('bar')
    return
  }
  console.log('NUMBER')
}

We check if num can be divided by 14 evenly with num % 14 === 0.

If it is, we log 'foobar'.

Similarly, we do the same checks when dividing num by 7 and 2 and log different values.

Otherwise, we log 'NUMBER' if none of the conditions are true.

Conclusion

We can use the modulo operator to get the remainder of the left operand divided by the right one.

Categories
JavaScript Answers

How to get div tag scroll position using JavaScript?

Sometimes, we want to get div tag scroll position using JavaScript.

In this article, we’ll look at how to get div tag scroll position using JavaScript.

How to get div tag scroll position using JavaScript?

To get div tag scroll position using JavaScript, we can use the scrollTop property.

For instance, we write:

<div style='height: 100px; overflow-y: auto'>
  <p>hello</p>
  <p>hello</p>
  <p>hello</p>
  <p>hello</p>
  <p>hello</p>
  <p>hello</p>
  <p>hello</p>
  <p>hello</p>
</div>

to add a scrollable div.

Then we write:

const div = document.querySelector('div')
div.addEventListener('scroll', () => {
  console.log(div.scrollTop)
})

to select the div with document.querySelector.

Then we call div.addEventListener with 'scroll' to add a scroll event listener.

And in the listener, we log the value of div.scrollTop.

Now when we scroll the div up and down, we should see the scroll position of the div in pixels.

Conclusion

To get div tag scroll position using JavaScript, we can use the scrollTop property.