Text editing web app

Question

try {
 var isSupported = !! new Blob();
} catch (e) {
 document.body.innerHTML = "<h1>Sorry your browser isn\'t supported :(</h1>";
}
var textarea = document.getElementById("textarea"),
 inputFile = document.getElementById("input-file"),
 appname = "notepad",
 untitled = "untitled.txt",
 isModified = false,
 filename;
window.onload = function() {
 if (localStorage.getItem("txt")) { // Load localStorage
 newNote(localStorage.getItem("txt"), localStorage.getItem("name"));
 } else {
 newNote();
 }
};
window.onunload = function() {
 if (isModified) { // Save localStorage
 localStorage.setItem("txt", textarea.value);
 localStorage.setItem("name", filename);
 } else {
 localStorage.clear();
 }
};
textarea.addEventListener("input", function() {
 isModified = true;
});
function changeDocTitle(newFilename) { // Change doc title
 filename = newFilename;
 document.title = filename + " - " + appname;
}
function dontSave() { // Confirm dont save
 if (confirm("You have unsaved changes that will be lost.")) {
 isModified = false;
 return true;
 }
}
function newNote(txt, name) { // New
 if (!isModified || dontSave()) {
 textarea.value = txt || "";
 changeDocTitle(name || untitled);
 if (textarea.value) {
 isModified = true;
 }
 }
 textarea.focus();
}
function openNote() { // Open
 if (!isModified || dontSave()) {
 inputFile.click();
 }
 textarea.focus();
}
inputFile.addEventListener("change", function() { // Load file
 var file = inputFile.files[0],
 reader = new FileReader();
 reader.onload = function() {
 newNote(reader.result, file.name);
 };
 reader.readAsText(file);
});
function rename() { // Rename
 var newFilename = prompt("Name this note:", filename);
 if (newFilename !== null) {
 if (newFilename === "") {
 changeDocTitle(untitled);
 } else {
 changeDocTitle(newFilename.lastIndexOf(".txt") == -1 ? newFilename + ".txt" : newFilename);
 }
 return true;
 }
}
function saveNote() { // Save
 if (rename()) {
 var blob = new Blob([textarea.value.replace(/\n/g, "\r\n")], {
 type: "text/plain;charset=utf-8"
 });
 saveAs(blob, filename);
 isModified = false;
 }
 textarea.focus();
}
function getStats() { // Stats
 var txt = textarea.value,
 txtStats = {};
 txtStats.chars = txt.length;
 txtStats.words = txt.split(/\S+/g).length - 1;
 txtStats.lines = txt.replace(/[^\n]/g, "").length + 1;
 return txtStats.lines + " lines, " + txtStats.words + " words, " + txtStats.chars + " chars";
}
document.addEventListener("keydown", function(e) { // Shortcuts
 var key = e.keyCode || e.which;
 if (e.altKey && e.shiftKey && key == 78) { // Alt+Shift+N
 e.preventDefault();
 newNote();
 }
 if (e.ctrlKey) { // Ctrl+
 switch (key) {
 case 79: // O
 e.preventDefault();
 openNote();
 break;
 case 83: // S
 e.preventDefault();
 saveNote();
 break;
 case 75: // K
 e.preventDefault();
 alert(getStats());
 break;
 case 191: // /
 e.preventDefault();
 alert("Help note for " + appname + " will be added soon!");
 break;
 }
 }
 if (key == 9) { // Tab
 e.preventDefault();
 var sStart = textarea.selectionStart,
 txt = textarea.value;
 textarea.value = txt.substring(0, sStart) + "\t" + txt.substring(textarea.selectionEnd);
 textarea.selectionEnd = sStart + 1;
 }
});

Answer 1

From a once over:

• You do not need the \ in "<h1>Sorry your browser isn\'t supported :(</h1>" because your string is surrounded with double quotes
• I would check immediately whether textarea and inputFile found something and give a proper error message when those elements are missing in the HTML
• You are doing both proper event handling with textarea.addEventListener and old skool event handling with window.onload, stick to proper event handling
• "txt" and "name" are the keys to interact with localStorage, these should be named constants
• Personally, I would try also to store the cursor position when storing the text in localStorage, this would look nice
• dontSave() { // Confirm dont save -> perhaps the function should be named differently ;)
• saveAs is missing ?

All in all a promising start for a cool editor. It helped me to build a jsbin for this : http://jsbin.com/jetuh/1/edit