DataTransferItemList: length-Eigenschaft
Baseline
Widely available
This feature is well established and works across many devices and browser versions. It’s been available across browsers since November 2016.
Die schreibgeschützte length-Eigenschaft des DataTransferItemList-Interfaces gibt die Anzahl der Elemente in der aktuellen Drag-Item-Liste zurück.
Wert
Die Anzahl der Drag-Daten-Elemente in der Liste oder 0, wenn die Liste leer oder deaktiviert ist. Die Drag-Item-Liste gilt als deaktiviert, wenn das DataTransfer-Objekt der Item-Liste nicht mit einem Drag-Datenspeicher verknüpft ist.
Beispiele
Dieses Beispiel zeigt die Verwendung der length-Eigenschaft.
HTML
html
<div>
<p id="source" draggable="true">
Select this element, drag it to the Drop Zone and then release the selection
to move the element.
</p>
</div>
<div id="target">Drop Zone</div>
CSS
css
div {
margin: 0em;
padding: 2em;
}
#source {
color: blue;
border: 1px solid black;
}
#target {
border: 1px solid black;
}
JavaScript
js
const source = document.getElementById("source");
const target = document.getElementById("target");
source.addEventListener("dragstart", (ev) => {
console.log("dragStart");
// Add this element's id to the drag payload so the drop handler will
// know which element to add to its tree
const dataList = ev.dataTransfer.items;
dataList.add(ev.target.id, "text/plain");
// Add some other items to the drag payload
dataList.add("<p>Paragraph…</p>", "text/html");
dataList.add("http://www.example.org", "text/uri-list");
});
source.addEventListener("dragend", (ev) => {
console.log("dragEnd");
const dataList = ev.dataTransfer.items;
// Clear any remaining drag data
dataList.clear();
});
target.addEventListener("drop", (ev) => {
console.log("Drop");
ev.preventDefault();
const data = ev.dataTransfer.items;
// Loop through the dropped items and log their data
for (let i = 0; i < data.length; i++) {
if (data[i].kind === "string" && data[i].type.match("^text/plain")) {
// This item is the target node
data[i].getAsString((s) => {
ev.target.appendChild(document.getElementById(s));
});
} else if (data[i].kind === "string" && data[i].type.match("^text/html")) {
// Drag data item is HTML
data[i].getAsString((s) => {
console.log(`… Drop: HTML = ${s}`);
});
} else if (
data[i].kind === "string" &&
data[i].type.match("^text/uri-list")
) {
// Drag data item is URI
data[i].getAsString((s) => {
console.log(`… Drop: URI = ${s}`);
});
}
}
});
target.addEventListener("dragover", (ev) => {
console.log("dragOver");
ev.preventDefault();
// Set the dropEffect to move
ev.dataTransfer.dropEffect = "move";
});
Ergebnis
Spezifikationen
| Specification |
|---|
| HTML # dom-datatransferitemlist-length-dev |
Browser-Kompatibilität
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