Determining the nature of dragged content in a Javascript dragenter event: distinguishing between text and files

Question

Determining the nature of dragged content in a Javascript dragenter event: distinguishing between text and files

When utilizing the dragenter event to display a dropzone for quickly uploading dropped files on the website, everything functions correctly. However, the dropzone also appears when dragging selected text. How can I differentiate between the two situations early on?

I am aware that the drop event provides access to all file contents through dataTransfer.files for iteration, but this is too late. I need this information at dragenter, yet I always find the files array to be empty.
I require complete control over the appearance and functionality and do not want to rely on an existing library.
I have noticed varying values for event.dataTransfer.Clipboard.effectAllowed when dragging text as opposed to files, with these values also differing between browsers (Chrome vs Firefox).
MooTools is being used, in case that information is helpful.

javascript file-upload drag-and-drop dom-events

Answer 1

Answer №1

After some trial and error, I managed to successfully implement drag and drop functionality in Chrome and Firefox (3.6+). While it may not be perfect, I wanted to share the code for anyone who could benefit from it:

  var isFileTransfer = false;
  if (evt.dataTransfer.types) {
    for (var i=0; i<evt.dataTransfer.types.length; i++) {
      if (evt.dataTransfer.types[i] == "Files") {
        isFileTransfer = true;
        break;
      }
    }
  }

Answer 2

After some trial and error, I managed to successfully implement drag and drop functionality in Chrome and Firefox (3.6+). While it may not be perfect, I wanted to share the code for anyone who could benefit from it:

  var isFileTransfer = false;
  if (evt.dataTransfer.types) {
    for (var i=0; i<evt.dataTransfer.types.length; i++) {
      if (evt.dataTransfer.types[i] == "Files") {
        isFileTransfer = true;
        break;
      }
    }
  }

Answer 3

Answer №2

To distinguish between a file being dragged into the browser from external sources and an image being dragged within the browser window, I utilized an approach involving event listeners for dragstart on the document object. When a file is dragged into the browser from outside, the dragstart event does not trigger. Therefore, detecting the firing of dragstart indicates that something is being dragged from within the same page.

document.addEventListener('dragstart', function() {
    samePageDrag = true;
}, false);

document.addEventListener('dragend', function() {
    if (samePageDrag) {
        samePageDrag = false;
    }
}, false);

This method allows you to assess the value of the samePageDrag variable after a dragenter or dragover event in order to ascertain whether the item being dragged originates from inside or outside the browser.

Answer 4

To distinguish between a file being dragged into the browser from external sources and an image being dragged within the browser window, I utilized an approach involving event listeners for dragstart on the document object. When a file is dragged into the browser from outside, the dragstart event does not trigger. Therefore, detecting the firing of dragstart indicates that something is being dragged from within the same page.

document.addEventListener('dragstart', function() {
    samePageDrag = true;
}, false);

document.addEventListener('dragend', function() {
    if (samePageDrag) {
        samePageDrag = false;
    }
}, false);

This method allows you to assess the value of the samePageDrag variable after a dragenter or dragover event in order to ascertain whether the item being dragged originates from inside or outside the browser.

Answer 5

Answer №3

For more information, please refer to the documentation available at: https://developer.mozilla.org/en-US/docs/Web/API/DataTransfer/types

If there are any files included in the drag operation, one of the types will be identified as the string Files.

This solution can be implemented in a single line of code

// Returns true if the dragged item is not a file
// Returns false if the dragged item is a file
event.dataTransfer.types.indexOf('Files') === -1

// Returns true if the dragged item is a file
// Returns false if the dragged item is not a file
event.dataTransfer.types.indexOf('Files') !== -1

Answer 6

For more information, please refer to the documentation available at: https://developer.mozilla.org/en-US/docs/Web/API/DataTransfer/types

If there are any files included in the drag operation, one of the types will be identified as the string Files.

This solution can be implemented in a single line of code

// Returns true if the dragged item is not a file
// Returns false if the dragged item is a file
event.dataTransfer.types.indexOf('Files') === -1

// Returns true if the dragged item is a file
// Returns false if the dragged item is not a file
event.dataTransfer.types.indexOf('Files') !== -1

Answer 7

Answer №4

I created a simple function to identify when files are being dragged.

function checkForFileTransfer(evt){
    return [].some.call(evt.dataTransfer.types,function(t){return t=="Files";});
}

Answer 8

I created a simple function to identify when files are being dragged.

function checkForFileTransfer(evt){
    return [].some.call(evt.dataTransfer.types,function(t){return t=="Files";});
}

Determining the nature of dragged content in a Javascript dragenter event: distinguishing between text and files

Answer №1

Answer №2

Answer №3

Answer №4

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