Category: JavaScript Answers

Sometimes, we want to reset all checkboxes using jQuery.

In this article, we’ll look at how to reset all checkboxes using jQuery.

How to reset all checkboxes using jQuery?

To reset all checkboxes using jQuery, we can remove the checked attribute of all checkboxes with prop.

For instance, we write:

<input type='checkbox'>
<input type='checkbox'>
<input type='checkbox'>
<button>
  reset
</button>

to add some checkboxes and a reset button.

Then we write:

$('button').click(() => {
  $('input[type=checkbox]').prop('checked', false);
})

We select the button with $.

And we call click with a click event handler callback.

In the callback, we select all the checkboxes and call prop with 'checked' and false to uncheck all checkboxes.

Conclusion

To reset all checkboxes using jQuery, we can remove the checked attribute of all checkboxes with prop.

Sometimes, we want to clone a JavaScript ES6 class instance.

In this article, we’ll look at how to clone a JavaScript ES6 class instance.

How to clone a JavaScript ES6 class instance?

To clone a JavaScript ES6 class instance, we can use the Object.assign, Object.create, and Object.getPrototypeOf methods.

For instance, we write:

class Foo {}

const orig = new Foo()
const clone = Object.assign(Object.create(Object.getPrototypeOf(orig)), orig)
console.log(clone)

We create a Foo class with class Foo {}.

Then we create an instance of that with new and assign it to orig.

Next, we call Object.prototypeOf with orig to get the prototype of orig.

And we call Object.create with that to create a new object with the same prototype as orig.

And then we merge that with the orig object itself with Object.assign and assign the returned object to clone.

Therefore, clone is also an instance of Foo and inherits from the same prototype.

Conclusion

To clone a JavaScript ES6 class instance, we can use the Object.assign, Object.create, and Object.getPrototypeOf methods.

Sometimes, we want to capture div into image using html2canvas.

In this article, we’ll look at how to capture div into image using html2canvas.

How to capture div into image using html2canvas?

To capture div into image using html2canvas, we can use the html2canvas function to return a promise with the canvas with the captured element content.

For instance, we write:

<script src="https://cdnjs.cloudflare.com/ajax/libs/html2canvas/1.3.2/html2canvas.min.js">
</script>

<div id='hello'>
  hello world
</div>

to add a div.

Then we write:

(async () => {
  const div = document.getElementById('hello')
  const canvas = await html2canvas(div)
  document.body.appendChild(canvas)
})()

We select the div with document.getElementById.

Then we call html2canvas with div to capture the div’s content into a canvas.

And finally, we call document.body.appendChild with canvas to attach the captured canvas into the body.

Now we should see an image version of the div displayed.

Conclusion

To capture div into image using html2canvas, we can use the html2canvas function to return a promise with the canvas with the captured element content.

Sometimes, we want to read line by line of a text area HTML element.

In this article, we’ll look at how to read line by line of a text area HTML element.

How to read line by line of a text area HTML element?

To read line by line of a text area HTML element, we can use the value property of the text area.

For instance, we write:

<textarea></textarea>

to add the text area.

Then we write:

const textarea = document.querySelector('textarea')

textarea.addEventListener('change', () => {
  const arrayOfLines = textarea.value.split("\n");
  for (const a of arrayOfLines) {
    console.log(a)
  }
})

We select the textarea with document.querySelector.

Then we call addEventListener to listen to the change event.

In the change event listener, we get the entered value string with textarea.value.

Then we call split with '\n' to split the string by the newline character into an array of strings.

And then we loop through each line with the for-of loop.

Conclusion

To read line by line of a text area HTML element, we can use the value property of the text area.

Sometimes, we want to check if file input is empty in JavaScript.

In this article, we’ll look at how to check if file input is empty in JavaScript.

How to check if file input is empty in JavaScript?

To check if file input is empty in JavaScript, we can get the files.length property from the file input.

For instance, we write:

<input type='file' id='videoUploadFile'>

to add a file input.

Then we write:

if (document.getElementById("videoUploadFile").files.length === 0) {
  console.log("no files selected");
}

We select the file input with document.getElementById.

Then we use the files.length property to check if any files are selected.

If it returns 0, then no file is selected.

Conclusion

To check if file input is empty in JavaScript, we can get the files.length property from the file input.