Is there a function to deselect all text using JavaScript?

This worked incredibly easier for me ...

document.getSelection().collapseToEnd()

or

document.getSelection().removeAllRanges()

Credits: https://riptutorial.com/javascript/example/9410/deselect-everything-that-is-selected

For a textarea element with at least 10 characters the following will make a small selection and then after a second and a half deselect it:

var t = document.getElementById('textarea_element');
t.focus();
t.selectionStart = 4;
t.selectionEnd = 8;

setTimeout(function()
{
 t.selectionStart = 4;
 t.selectionEnd = 4;
},1500);