JSFiddle - React, Tailwind, and code Playground

HTML

<input type="file" id="fileInput" />
<input type="button" onClick="checkDeleted();" value="Check" />

JavaScript

function checkDeleted() {
    input = document.getElementById('fileInput');
    if (input.files.length > 0) {
        var file = input.files[0];
        var fr = new FileReader();
        fr.onload = function (e) {
            alert("File is readable");
        };
        fr.onerror = function (e) {
            if (e.target.error.name == "NotFoundError") {
                alert("File deleted");
            }
        }
        fr.readAsText(file);
    } else {
        // no file choosen yet
    }
}