Category: JavaScript Answers

Sometimes, we want to reload a page every 5 seconds in our web app.

In this article, we’ll look at how to reload a page every 5 seconds with JavaScript.

Using the setInterval Function

We can use the setInterval function to run code periodically.

It takes the callback with the code to run periodically as the first argument and the 2nd argument is the delay between each time the callback runs.

For instance, if we have:

<div>
  hello world
</div>

Then we can write:

setInterval(() => {
  window.location.reload();
}, 5000);

to call window.location.reload event 5 seconds.

The delay is in milliseconds so 5000 ms is 5 seconds.

Now we should see the page reload every 5 seconds.

Conclusion

We can use the setInterval function to run code to reload the page periodically.

window.location.reload() will reload the page.

Sometimes, we may want to scroll to the top of a browser page with JavaScript.

In this article, we’ll look at how to scroll to the top of a browser page with JavaScript.

Use the window.scrollTo Method

We can use the window.scrollTo method with the x and y coordinates to scroll to as arguments respectively.

For instance, if we have the following HTML:

<div>

</div>
<button>
  scroll to top
</button>

Then we can write the following JavaScript to add child elements to the div and make the button scroll to the top of the page by writing:

const button = document.querySelector('button')
const div = document.querySelector('div')
for (let i = 0; i < 100; i++) {
  const p = document.createElement('p')
  p.textContent = i
  div.appendChild(p)
}

button.addEventListener('click', () => {
  window.scrollTo(0, 0);
})

We have the for loop to add elements with document.createElement .

And then we set the textContent to some content.

Then we call appendChild to add the elements.

Next, we call button.addEventListener with 'click' to add a click listener.

We call scrollTo with 0 and 0 to scroll to the top of the page.

So when we click on ‘scroll to top’, we should go to the top of the page.

We can also change the scroll behavior with an object to change the scroll behavior.

For instance, we can write:

button.addEventListener('click', () => {
  window.scrollTo({
    top: 0,
    behavior: `smooth`
  })
})

top is set to 0 to scroll to the top.

behavior is set to 'smooth' to make the scrolling smooth.

Conclusion

We can scroll to the top of the page with the window.scrollTo method.

Sometimes, we may want to adjust the width of an input field to the width of its input value.

In this article, we’ll look at how to adjust the width of an input field to the width of its input value.

Listen to the keypress Event

We can listen to the keypress event to get the input value on keypress.

Then we can set the style.width property of the input to the width of the input value.

To do this, we write the following HTML:

<input type="text">

And the following JavaScript:

const input = document.querySelector('input')
input.addEventListener('keypress', (e) => {
  input.style.width = `${e.target.value.length}ch`
})

We get the input element with querySelector .

Then we call addEventListener with 'keypress’ to listen to the keypress event.

In the event handler callback, we set input.style.width to the e.target.value.length with unit in ch .

e.target.value has the value inputted into the input box.

ch is the width of the 0 character of the element’s font.

Now when we type in the input, we should see the input box lengthen to the width of the input value as we type stuff in.

Conclusion

We can set an input element’s width to the width of the inputted value setting the width of the input in ch .

Sometimes, we may want to change the selected drop-down option with JavaScript.

In this article, we’ll look at how to change an HTML selected option with JavaScript.

Set the value Property of the Select Drop Down

We can change the HTML select element’s selected option with JavaScript by setting the value property of the select element object.

For instance, we can write the following HTML:

<select>
  <option value="apple">Apple</option>
  <option value="orange">Orange</option>
  <option value="grape">Grape</option>
</select>

<button id='apple'>
  apple
</button>
<button id='orange'>
  orange
</button>

We have a select drop down with some options and 2 buttons that sets the selected options when clicked.

Then we can add the following JavaScript code to set the options with the buttons:

const appleBtn = document.getElementById('apple')
const orangeBtn = document.getElementById('orange')
const select = document.querySelector('select')

appleBtn.addEventListener('click', () => {
  select.value = 'apple'
})

orangeBtn.addEventListener('click', () => {
  select.value = 'orange'
})

We get the 2 buttons with getElementById .

And we get the select drop down with querySelector .

Then we call addEventListener with 'click' to add click listeners on the buttons.

And we set select.value of each to the value that we want to select.

value should be set to the value of the value attribute for this to work.

Now when we click the buttons, we should see the selected value in the drop-down change to one we set in the click listener.

Conclusion

We can set the select option with the HTML select dropdown with JavaScript by setting the value property.

Sometimes, we want to convert a JavaScript string into camel case with JavaScript.

In this article, we’ll look at how to convert any string into camel case with JavaScript.

Use the String.prototype.replace method

We can use the string instances’ replace method to convert each word in the string to convert the first word to lower case, the rest of the words to upper case, then remove the whitespaces.

To do this, we write:

const camelize = (str) => {
  return str.replace(/(?:^\w|\[A-Z\]|\b\w)/g, (word, index) => {
    return index === 0 ? word.toLowerCase() : word.toUpperCase();
  }).replace(/\s+/g, '');
}
`
console.log(camelize("EquipmentClass name"));

We call replace with a regex that looks for word boundaries with \b and \w .

\b matches a backspace.

\w matches any alphanumeric character from the Latin alphabet.

We check the index to determine if it’s the first word or not.

If it’s 0, then we return word.toLowerCase() to convert it first character of the word to lower case since it’s the first word.

Otherwise, we return word.toUpperCase to convert the first character of the word to upper case.

Then we call replace again with /\s+/g and an empty string to replace the spaces with empty strings.

Therefore, camelize returns 'equipmentClassName’ as a result.

Lodash camelCase Method

We can use the Lodash camelCase method to convert any string to camel case the same way the camelize function does.

For instance, we can write:

console.log(_.camelCase("EquipmentClass name"));

Then we get the same result as the previous example.

Conclusion

We can convert any JavaScript string to camel case with the String.prototype.replace method or the Lodash camelCase method.