changing label on bootstrap custom upload file input field

uploadname.js

//bootstrap 4 custom upload
//<input type="file" name="fileToUpload" id="fileToUpload" accept=".pdf" class="custom-file-input" onchange="getname(event)">
//<label class="custom-file-label file-upload-info" for="fileToUpload" id="upload_label">Upload PDF</label>

//uploaded filename > label, default label is back on clear;

let deflabel = "Upload File";
if (document.getElementById("upload_label")) deflabel = document.getElementById("upload_label").innerHTML;
function getname(evt){
	//console.log(evt);
	var filename;
	var files = evt.target.files;	
	if (files.length > 0) {
		filename = files[0].name;
	} else {
		filename = deflabel;
	}
	document.getElementById("upload_label").innerHTML = filename;
}