Category: JavaScript Answers

Sometimes, we want to get an element’s nth-child element in JavaScript.

In this article, we’ll look at how to get an element’s nth-child element in JavaScript.

How to get an element’s nth-child element in JavaScript?

To get an element’s nth-child element in JavaScript, we can use querySelector.

For instance, we write:

<section class="hardware">some text, nth-child is one</section>
<section class="hardware">some text, nth-child is two</section>
<section class="hardware">some text, nth-child is three</section>
<section class="hardware">some text, nth-child is four</section>
<section class="hardware">some text, nth-child is five</section>

to add 5 section elements.

Then we get the 2nd section element by writing:

const child = document.querySelector('.hardware:nth-child(2)')
console.log(child)

We call document.querySelector with '.hardware:nth-child(2)' to get the 2nd section element with class hardware.

Therefore, child is <section class="hardware">some text, nth-child is two</section>.

Conclusion

To get an element’s nth-child element in JavaScript, we can use querySelector.

Sometimes, we want to get the index of item in a JavaScript set.

In this article, we’ll look at how to get the index of item in a JavaScript set.

How to get the index of item in a JavaScript set?

To get the index of item in a JavaScript set, we can convert the set into an array and then use the array indexOf method.

For instance, we write:

const s = new Set([1, 2, 3])
const index = [...s].indexOf(2)
console.log(index)

to create a set with the Set constructor.

Then we spread the set s into an array with the spread operator.

Next, we call indexOf on the array with the value we want to find the index for.

Therefore, index is 1.

Conclusion

To get the index of item in a JavaScript set, we can convert the set into an array and then use the array indexOf method.

Sometimes, we want to prevent select on input text field with JavaScript.

In this article, we’ll look at how to prevent select on input text field with JavaScript.

How to prevent select on input text field with JavaScript?

To prevent select on input text field with JavaScript, we can set the input’s selectionStart property to the value of the input’s selectionEnd property.

For instance, we write:

<input>

to add an input.

Then we write:

const input = document.querySelector('input');
input.onselect = (e) => {
  e.target.selectionStart = e.target.selectionEnd;
}

to select the input with querySelector.

Then set the input.onselect property to a function that sets e.target.selectionStart to e.target.selectionEnd to set the selection range to length 0 to prevent selection.

Conclusion

To prevent select on input text field with JavaScript, we can set the input’s selectionStart property to the value of the input’s selectionEnd property.

Sometimes, we want to limit array size with JavaScript.

In this article, we’ll look at how to limit array size with JavaScript.

How to limit array size with JavaScript?

To limit array size with JavaScript, we can use the array slice method.

For instance, we write:

const arr = [1, 2, 3]
const add = (a, x) => [x, ...a.slice(0, a.length - 1)];
console.log(add(arr, 4))

to define the add function that takes an array a and value x that we prepend to the returned array.

We keep the returned array the same size as a by calling slice with 0 and a.length - 1 to discard the last item in a.

Therefore, the console log logs [4, 1, 2].

Conclusion

To limit array size with JavaScript, we can use the array slice method.

Sometimes, we want to make a checkbox without a form with HTML and JavaScript.

In this article, we’ll look at how to make a checkbox without a form with HTML and JavaScript.

How to make a checkbox without a form with HTML and JavaScript?

To make a checkbox without a form with HTML and JavaScript, we can add an input element with type checkbox.

Then we can get its value when we check or uncheck it by attaching a change event handler to it.

For instance, we write:

<input type="checkbox" />

to add an input with the type attribute set to checkbox to add a checkbox.

Then we write:

const input = document.querySelector('input')
input.onchange = (e) => {
  console.log(e.target.checked)
}

to select the input with querySelector.

Then we set the input.onchange property to a function that gets the checked value of the checkbox from e.target.checked.

Conclusion

To make a checkbox without a form with HTML and JavaScript, we can add an input element with type checkbox.

Then we can get its value when we check or uncheck it by attaching a change event handler to it.