Drag and Drop the default value?

In the second line of ev.preventDefault(); prevent the work handler by default, it is not clear what it does by default
function allowDrop(ev) {
ev.preventDefault();
}

function drag(ev) {
 ev.dataTransfer.setData("text", ev.target.id);
}

function drop(ev) {
ev.preventDefault();
 var data = ev.dataTransfer.getData("text");
ev.target.appendChild(document.getElementById(data));
}


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June 8th 19 at 17:02

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