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Display message if array is empty

I'm displaying favorites from localStorage on a page and I'd like to display a message for people that don't have any favorites yet.
This is the div that displays the list which I'd like to repurpose to display the message below when there are no favorites:
<div id='favorites'></div>
And here is the JavaScript that normally shows the favorites:
var options = Array.apply(0, new Array(localStorage.length)).map(function (o, i){
return localStorage.key(i);
});
function makeUL() {
var LIs = '';
var noFavs = 'Hmm, you must\'ve not favorited anything yet. Maybe you\'ll like this one.';
var len = options.length;
if (len === 0) {
document.getElementById('nofavorites').innerHTML = noFavs;
} else {
for (i = 0; i < len; i += 1) {
LIs += '<li>' + options[i] + '</li>';
}
return '<ul>' + LIs + '</ul>';
}
}
document.getElementById('favorites').innerHTML = makeUL();
Right now it just shows undefined.

This is in your html:
<div id='favorites'></div>
<div id='nofavorites'></div>
Your javascript:
var options = Array.apply(0, new Array(localStorage.length)).map(function (o, i){
return localStorage.key(i);
});
function loadFavoriteHTML() {
var favoriteHtml = '';
var noFavs = 'Hmm, you must\'ve not favorited anything yet. Maybe you\'ll like this one.';
var len = options.length;
// Clear html lists
document.getElementById('favorites').innerHTML = '';
document.getElementById('nofavorites').innerHTML = '';
if (len === 0) {
document.getElementById('nofavorites').innerHTML = noFavs;
} else {
for (var i = 0; i < len; i++) {
favoriteHtml+= '<li>' + options[i] + '</li>';
}
var ulHtml= '<ul>' + favoriteHtml+ '</ul>';
document.getElementById('favorites').innerHTML = ulHtml;
}
}
loadFavoriteHTML();
Your code is show undefine because when you dont have favorites list you dont return anything in you makeUI function, and by default the return value is undefined in a function if you dont have return.
I changed your code to set the UI in the function because you edit 2 different div. there is others way to do it. this is a one way.

It's because the makeUL function doesn't return any value when there's no element in the options array.
You'll have to choose between: updating your element inside your function
OR getting the value to insert inside your HTML element returned by your function. But you shouldn't do both.
You might want to change your code into something like this?
var options = Array.apply(0, new Array(localStorage.length)).map(function (o, i) {
return localStorage.key(i);
});
function makeUL() {
var LIs = '';
var noFavs = 'Hmm, you must\'ve not favorited anything yet. Maybe you\'ll like this one.';
var len = options.length;
if (len === 0) {
document.getElementById('favorites').innerHTML = noFavs;
} else {
for (var i = 0; i < len; i += 1) {
LIs += '<li>' + options[i] + '</li>';
}
document.getElementById('favorites').innerHTML = '<ul>' + LIs + '</ul>';
}
}
makeUL();
Plus, you're targeting a nofavorites element that doesn't exist in your example.

Dynamically load images, break loop on error

I asked this previously but didn't get an answer that applied to my project. I am trying to load images to a table dynamically without having to use server side code. It works, but I want to be able to have an infinite loop that breaks when a picture fails to load, rather than hard code the number of rows I need. That way I won't ever have to update the code, I'll just be able to add pictures to a folder if I want to expand the table.
Right now the "onerror" attribute hides the failed image, but I also want to break out of the outer loop (loop1).
function headCatalogLoader() {
var table = document.getElementById("catalog");
var meshNum = 0;
var uniqueID = 0;
loop1:
for (var i = 0; i <= 50; i++) { // i made it 50 instead of infinite for now
var row = table.insertRow(i);
loop2:
for (var k = 0; k <= 2; k++) { // 2 is because 3 columns
var skinTone = "none";
var cell = row.insertCell(k);
if (k == 0) {
skinTone = "lgt";
}
else if (k == 1) {
skinTone = "med";
}
else if (k == 2) {
skinTone = "drk";
}
cell.innerHTML = "<img src=\"headimgs/head" + skinTone + meshNum + ".png\" id=\"head" + uniqueID + skinTone + "\" onclick=\"previewIt(this)\" onerror=\"$(this).hide();\" />";
uniqueID++;
}
meshNum++;
}
var tbody = $("table tbody");
tbody.html($("tr",tbody).get().reverse());
}
Breaking from within the attribute is out of the loop's scope and doesn't work. Also using
$('img').on("error", function () {
break loop1;
});
inside loop2 doesn't do anything. Someone suggested I use a recursive method and rewrite my function, but that won't work for me since I'm dynamically creating a table and using image names that correspond to the loop. Any help or suggestions would be wonderful!

I'm thinking you could use an XMLHttpRequest to check the response for that URL before trying to put it onto the page. If status is not 404 then insert image else break loop1. Something like this might work:
function headCatalogLoader() {
var table = document.getElementById("catalog");
var meshNum = 0;
var uniqueID = 0;
loop1:
for (var i = 0; i <= 50; i++) { // i made it 50 instead of infinite for now
var row = table.insertRow(i);
loop2:
for (var k = 0; k <= 2; k++) { // 2 is because 3 columns
var skinTone = "none";
var cell = row.insertCell(k);
if (k == 0) {
skinTone = "lgt";
} else if (k == 1) {
skinTone = "med";
} else if (k == 2) {
skinTone = "drk";
}
// note: you'll need to use an absolute path for imageUrl
var imageUrl = "http://example.co.uk/example/headimgs/head" + skinTone + meshNum + ".png";
var xhttp = new XMLHttpRequest();
xhttp.open('HEAD', imageUrl, false);
xhttp.send();
if (xhttp.status !== 404) {
cell.innerHTML = "<img src=" + imageUrl + " id=\"head" + uniqueID + skinTone + "\" onclick=\"previewIt(this)\" onerror=\"$(this).hide();\" />";
uniqueID++;
} else {
break loop1;
}
}
meshNum++;
}
var tbody = $("table tbody");
tbody.html($("tr", tbody).get().reverse());
}
Note: you'll need to use an absolute path for the XMLHttpRequest. I've just used example.co.uk/example because I don't know your URL.
I'm guessing you're only expecting it to error if the image is not found, because that would indicate that you've reached the last image in your folder, which is why I checked !== 404, if you want to break in the case of any error (such as 500 internal server error), it might be best to change if (xhttp.status !== 404) to if (xhttp.status === 200).

Add certain values from JSON object to javascript array

Update: I've tried the suggestions in the comments and it's still not working. I really have no idea why. I've consolidated it to a single loop and fixed the syntax errors noted. Here's the code as it looks now:
$(function() {
$("#json-one").change(function() {
var $dropdown = $(this);
$.getJSON("washroutines.json", function(data) {
var vals = [];
var $jsontwo = $("#json-two");
$jsontwo.empty();
for (var i = 0; i < data.length; i++){
if (data[i].make === $dropdown.val()) {
$jsontwo.append("<option value=\"" + data[i].model + "\">" + data[i].model + "</option>");
}
}
});
});
});
Any additional help would be much appreciated!
Original question:
I'm trying to create dependent drop down menus using a json object, and I'm having trouble getting the second menu to populate based on the first. When the first menu changes, the second goes to a bunch of "undefined"s.
$.getJSON("washroutines.json", function(data) {
var vals = [];
for (i = 0; i < data.length; i++){
if (data.make = $dropdown.val()) {
vals.push(data.model);
}
}
var $jsontwo = $("#json-two");
$jsontwo.empty();
for (i = 0; i < vals.length; i++){
$jsontwo.append("<option value\"" + vals[i] + "\">" + vals[i] + "</option>");
}
Please use small words when explaining things to me, I'm new at this!
contents of the JSON:
[{"make":"Maytag","model":"Bravos","prewashCycle":"Whitest Whites"},
{"make":"Maytag","model":"Awesome","prewashCycle":"Awesome Whitest Whites"},
{"make":"Whirlpool","model":"Cabrio","prewashCycle":"Extra Heavy"},
{"make":"Kenmore","model":"Elite","prewashCycle":"Awesome"}]

Try changing your for loop for this
for (var i = 0; i < data.length; i++){
if (data[i].make === $dropdown.val()) {
vals.push(data[i].model);
}
}

Java Script add value of variable to object property?

I'm new here and to JavaScript. I have an assignment that asks "create a new property in the foodInfo object plus the value of the toppings variable, and set the ne property's value to to value of the current element in the toppingBoxes array."
Here is the code I have that is not working, I have tried multiple things but cant get it to print out the toppings on the page:
for (var i = 0; i < toppingBoxes.length; i++) {
if (toppingBoxes[i].checked) {
toppings = toppings + 1;
foodInfo.topping[toppings] = toppingBoxes[i].value;
}
}
Here is the code the assignment gave me to print it, so this code is correct, but the code above is what I need help with:
foodSummary.innerHTML += "<ul>";
for (var i = 1; i < 6; i++) {
if (foodInfo["topping" + i]) {
foodSummary.innerHTML += "<li>" + foodInfo["topping" + i] + "</li>";
}
}
foodSummary.innerHTML += "</ul>";
I know the code stops running when it hits the line "foodInfo.topping[toppings] = toppingBoxes[i].value;" so I know that is wrong. I am having trouble with the instructions I mentioned above...any help to get this working? Thank you in advance!!

Try this:
var toppings = 0;
for (var i = 0; i < toppingBoxes.length; i++) {
if (toppingBoxes[i].checked) {
toppings = toppings + 1;
foodInfo['toppings' + toppings] = toppingBoxes[i].value;
}
}

two delimiters output formatting javascript

I thought this would be easier, but running into a weird issue.
I want to split the following:
theList = 'firstword:subwordone;subwordtwo;subwordthree;secondword:subwordone;thirdword:subwordone;subwordtwo;';
and have the output be
firstword
subwordone
subwordtwo
subwordthree
secondword
subwordone
thirdword
subwordone
subwordtwo
The caveat is sometimes the list can be
theList = 'subwordone;subwordtwo;subwordthree;subwordfour;'
ie no ':' substrings to print out, and that would look like just
subwordone
subwordtwo
subwordthree
subwordfour
I have tried variations of the following base function, trying recursion, but either get into infinite loops, or undefined output.
function getUl(theList, splitOn){
var r = '<ul>';
var items = theList.split(splitOn);
for(var li in items){
r += ('<li>'+items[li]+'</li>');
}
r += '</ul>';
return r;
}
The above function is just my starting point and obviously doesnt work, just wanted to show what path I am going down, and to be shown the correct path, if this is totally off base.

It seems you need two cases, and the difference between the two is whether there is a : in your string.
if(theList.indexOf(':') == -1){
//Handle the no sublist case
} else {
//Handle the sublist case
}
Starting with the no sublist case, we develop the simple pattern:
var elements = theList.split(';');
for(var i = 0; i < elements.length; i++){
var element = elements[i];
//Add your element to your list
}
Finally, we apply that same pattern to come up with the implementation for the sublist case:
var elements = theList.split(';');
for(var i = 0; i < elements.length; i++){
var element = elements[i];
if(element.indexOf(':') == -1){
//Add your simple element to your list
} else {
var innerElements = element.split(':');
//Add innerElements[0] as your parent element
//Add innerElements[1] as your child element
//Increment i until you hit another element with ':', adding the single elements each increment as child elements.
//Decrement i so it considers the element with the ':' as a parent element.
}
}

Keep track of the current list to add items to, and create a new list when you find a colon in an item:
var baseParent = $('ul'), parent = baseParent;
$.each(theList.split(';'), function(i, e) {
if (e.length) {
var p = e.split(':');
if (p.length > 1) {
baseParent.append($('<li>').append($('<span>').text(p[0])).append(parent = $('<ul>')));
}
parent.append($('<li>').text(p[p.length - 1]));
}
});
Demo: http://jsfiddle.net/Guffa/eWQpR/
Demo for "1;2;3;4;": http://jsfiddle.net/Guffa/eWQpR/2/

There's probably a more elegant solution but this does the trick. (See edit below)
function showLists(text) {
// Build the lists
var lists = {'': []};
for(var i = 0, listKey = ''; i < text.length; i += 2) {
if(text[i + 1] == ':') {
listKey = text[i];
lists[listKey] = [];
} else {
lists[listKey].push(text[i]);
}
}
// Show the lists
for(var listName in lists) {
if(listName) console.log(listName);
for(var j in lists[listName]) {
console.log((listName ? ' ' : '') + lists[listName][j]);
}
}
}
EDIT
Another interesting approach you could take would be to start by breaking it up into sections (assuming text equals one of the examples you gave):
var lists = text.match(/([\w]:)?([\w];)+/g);
Then you have broken down the problem into simpler segments
for(var i = 0; i < lists.length; i++) {
var listParts = lists[i].split(':');
if(listParts.length == 1) {
console.log(listParts[0].split(';').join("\n"));
} else {
console.log(listParts[0]);
console.log(' ' + listParts[1].split(';').join("\n "));
}
}

The following snippet displays the list depending on your requirements
var str = 'subwordone;subwordtwo;subwordthree;';
var a = []; var arr = [];
a = str;
var final = [];
function split_string(a){
var no_colon = true;
for(var i = 0; i < a.length; i++){
if(a[i] == ':'){
no_colon = false;
var temp;
var index = a[i-1];
var rest = a.substring(i+1);
final[index] = split_string(rest);
return a.substring(0, i-2);
}
}
if(no_colon) return a;
}
function display_list(element, index, array) {
$('#results ul').append('<li>'+element+'</li>');
}
var no_colon_string = split_string(a).split(';');
if(no_colon_string){
$('#results').append('<ul><ul>');
}
no_colon_string.forEach(display_list);
console.log(final);
working fiddle here