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JavaScript Answers jQuery

How to Get the Context of a Canvas with jQuery?

Sometimes, we want to get the context of a Canvas with jQuery

In this article, we’ll look at how to get the context of a Canvas with jQuery.

Get the Context of a Canvas with jQuery

To get the context of a Canvas with jQuery, we call the get method with the index of the element we want to get.

Then we can call getContext on the returned element.

For instance, if we have the following canvas:

<canvas width='200' height='200'></canvas>

We write:

const ctx = $("canvas").get(0).getContext('2d');  
console.log(ctx)

to select canvas elements with $(“canvas”) .

Then we use get(0) to get the first canvas element selected.

And then we call getContext on that to get the context.

Conclusion

To get the context of a Canvas with jQuery, we call the get method with the index of the element we want to get.

Then we can call getContext on the returned element.

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JavaScript Answers jQuery

How to Handle Tab Key Presses in a Text Area with jQuery?

Sometimes, we want to handle tab key presses in a text area with jQuery.

In this article, we’ll look at how to handle tab key presses in a text area with jQuery.

Handle Tab Key Presses in a Text Area with jQuery

To handle tab key presses in a text area with jQuery, we can detect when the tab key is pressed in the text area.

Then if it’s pressed, we can call e.preventDefault on it to prevent the default behavior.

For instance, if we have the following text area:

<textarea></textarea>

Then we can listen to the keydown event to listen for tab key presses:

$("textarea").keydown((e) => {
  if (e.keyCode === 9) {
    const start = e.target.selectionStart;
    const end = e.target.selectionEnd;
    const $this = $(e.target);
    const value = $this.val();
    $this.val(`${value.substring(0, start)}\t${value.substring(end)}`);
    $this.selectionStart = $this.selectionEnd = start + 1;
    e.preventDefault();
  }
});

We get the text area with $(“textarea”) .

Then we call keydown to listen to the keydown event.

We pass in a callback to the keydown method.

In the callback, we check e.keyCode to check if it’s 9 to see if we pressed on tab or not.

If it’s true , then we pressed on tab.

In the if block, we get the start and end of the text selection with:

const start = e.target.selectionStart;
const end = e.target.selectionEnd;

Then assign the textarea element to $this with:

const $this = $(e.target);

We get the input value wit:

const value = $this.val();

And then we update the value of the text area by writing:

$this.val(`${value.substring(0, start)}t${value.substring(end)}`);

to insert a tab at the position where the selection is made.

Finally, we set the selection range with:

$this.selectionStart = $this.selectionEnd = start + 1;

to move the cursor to the end.

And finally, we call e.preventDefault to stop the default behavior, which is to move focus away from the text area.

Conclusion

To handle tab key presses in a text area with jQuery, we can detect when the tab key is pressed in the text area.

Then if it’s pressed, we can call e.preventDefault on it to prevent the default behavior.

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JavaScript Answers jQuery

How to Disable Right-Click on Images Using jQuery?

Sometimes, we want to disable right-click on images using jQuery.

In this article, we’ll look at how to disable right-click on images using jQuery.

Disable Right-Click on Images Using jQuery

To disable right-click on images using jQuery, we can listen to the contextmenu event on the image element.

Then in the event handler callback, we can return false to prevent right-clicks on images.

For instance, if we have the following image:

<img src='https://picsum.photos/200/300'>

Then we can write:

$('img').bind('contextmenu', (e) => {  
  return false;  
});

to get all image elements with $(‘img’) .

Then we call bind with 'contextmenu' to listen to the contextmenu event.

And in the event handler callback, we return false .

Now when we right-click on the image, we shouldn’t see any context menu displayed.

Conclusion

To disable right-click on images using jQuery, we can listen to the contextmenu event on the image element.

Then in the event handler callback, we can return false to prevent right-clicks on images.

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JavaScript Answers jQuery

How to Remove Hyphens from a JavaScript String?

Sometimes, we want to remove hyphens from a JavaScript string.

In this article, we’ll look at how to remove hyphens from a JavaScript string.

Remove Hyphens from a JavaScript String

To remove hyphens from a JavaScript string, we can call the JavaScript string’s replace method.

For instance, we can write:

const str = "185-51-671";  
const newStr = str.replace(/-/g, "");  
console.log(newStr)

We call replace with a regex that matches all dashes with /-/ .

The g flag matches all instances of the pattern.

Then we replace all of them with empty strings as specified in the 2nd argument.

Therefore, newStr is '18551671' .

Conclusion

To remove hyphens from a JavaScript string, we can call the JavaScript string’s replace method.

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JavaScript Answers jQuery

How to Add Infinite Scrolling with jQuery?

Sometimes, we want to add infinite scrolling with jQuery.

In this article, we’ll look at how to add infinite scrolling with jQuery.

Add Infinite Scrolling with jQuery

To add infinite scrolling with jQuery, we can detect when we scrolled to the bottom of the page with the scroll method.

To do this, we write the following HTML to contain our content:

<div id="lipsum">
</div>

Then we can add some content into the div when we scrolled to the bottom of the page by writing:

const arr = [...Array(30)].fill().map((_, i) => i)
for (const n of arr) {
  $('#lipsum').append(`<p>${n}</p>`)
}

$(window).scroll(() => {
  if ($(window).scrollTop() >= $(document).height() - $(window).height() - 10) {
    for (const n of arr) {
      $('#lipsum').append(`<p style='background-color: red'>${n}</p>`)
    }
  }
});

We first add some content to the div with:

const arr = [...Array(30)].fill().map((_, i) => i)
for (const n of arr) {
  $('#lipsum').append(`<p>${n}</p>`)
}

Then we detect when we scroll to the bottom of the page by calling $(window).scroll with a callback.

In the callback, we check if we scrolled to the bottom of the page with:

$(window).scrollTop() >= $(document).height() - $(window).height() - 10

And if that’s true , we add some content with the for-of loop.

scrollTop gets the scroll position of the page.

And $(document).height() — $(window).height() — 10 is the position at the bottom of the page in pixels.

Now we should see new content displayed when we scrolled to the bottom of the page.

Conclusion

To add infinite scrolling with jQuery, we can detect when we scrolled to the bottom of the page with the scroll method.