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Highlight an element when dragging a file over it

Written byPhuoc Nguyen
Category
Level 2 — Intermediate
Created
09 Mar, 2020
Assume that we have a droppable element as below
<div id="droppable">...</div>
We will hightlight the element when user drags a file over it. For example, the element will have a dashed border which can be simulated by a CSS class:
.dragging {
border: 4px dashed #ccc;
}
The `dragging` class will be added to the element when user drags file and moves it over the element:
// Query the element
const ele = document.getElementById('droppable');

ele.addEventListener('dragenter', function (e) {
e.preventDefault();
e.target.classList.add('dragging');
});
In similar events, the class is removed from the element when user moves the file out of the element, or drops it:
ele.addEventListener('dragover', function (e) {
e.preventDefault();
});

ele.addEventListener('dragleave', function (e) {
e.preventDefault();
e.target.classList.remove('dragging');
});

ele.addEventListener('drop', function (e) {
e.preventDefault();
e.target.classList.remove('dragging');
});
The last thing, `e.preventDefault()` is used in the handlers to prevent the browser from executing the default action.

Demo

See also

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Phước Nguyễn