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JS for loop not working

I have a for loop which looks like this:
for (var i = 0; i < list.length; i++) {
It is looping through Firebase data in the database and returning all the data in the database.
However, I want it to only go up to the first 10 database items. So I changed the loop to:
for (var i = 0; i < 9; i++) {
But this fails to display any results when the there are less than 10 pieces of data in the database. However, if I set the number to however many objects I have in the database, for example 10 because I have 10 objects, it displays them all. But any less than this number and I just get a blank webpage.
Here is the webpage when I have 10 objects in my Firebase database:
And here it is when I remove one of those objects:
I have no idea why this is happening - The logic is correct - if i is less than 9 then display the data - But instead it only displays it when it equals 9.
Here is the full JS:
function refreshUI(list) {
var lis = '';
var lis2 = '';
var lis3 = '';
var lis4 = '';
for (var i = 0; i <= 9; i++) {
lis += '<li data-key="' + list[i].key + '" onclick="addText(event)">' + list[i].book + '</li>';
lis2 += genLinks(list[i].key, list[i].book)
};
for (var i = 10; i < list.length; i++) {
lis3 += '<li data-key="' + list[i].key + '" onclick="addText(event)">' + list[i].book + '</li>';
lis4 += genLinks(list[i].key, list[i].book)
};
document.getElementById('bookList').innerHTML = lis;
document.getElementById('bookList2').innerHTML = lis2;
document.getElementById('bookList3').innerHTML = lis3;
document.getElementById('bookList4').innerHTML = lis4;
};
function genLinks(key, bkName) {
var links = '';
links += '<img src="images/bin.png" style="width: 24px; height: 24px; transform: translateY(-7px); opacity: .4;"></img> ';
return links;
};
function del(key, bkName) {
var response = confirm("Are certain about removing \"" + bkName + "\" from the list?");
if (response == true) {
// build the FB endpoint to the item in movies collection
var deleteBookRef = buildEndPoint(key);
deleteBookRef.remove();
}
}
function buildEndPoint (key) {
return new Firebase('https://project04-167712.firebaseio.com/books/' + key);
}
// this will get fired on inital load as well as when ever there is a change in the data
bookList.on("value", function(snapshot) {
var data = snapshot.val();
var list = [];
for (var key in data) {
if (data.hasOwnProperty(key)) {
book = data[key].book ? data[key].book : '';
if (book.trim().length > 0) {
list.push({
book: book,
key: key
})
}
}
}
// refresh the UI
refreshUI(list);
});
If anybody has any help I'd greatly appreciate it!

When the list size is shorter than 10, you will get an error in the loop because you will eventually address a property (like key) that does not exist on list[i] (since it is undefined). If you would check the console, you would notice that this error is reported.
To fix this, change the condition of the first for loop like this:
for (var i = 0; i < Math.min(10, list.length); i++) {
This way, the loop will never iterate to an entry that does not exist. It will stop after 9 or after list.length-1 whichever comes first.
Alternatively, you can just put the two conditions with an && operator:
for (var i = 0; i < 10 && i < list.length; i++) {

How to dynamically append data to a webpage after API call?

I am trying to create a webpage that, given a user input, returns a list of results from wikipedia. I have gotten the call to Wikipedia's API to work fine, but when I attempt to append the data to my webpage, it flickers on for a split second and then disappears. I suspect it has to do with the event handlers, but I have tried several alternatives without luck. I also looked around SO and the web at large but could not find a solution. Here is my code:
var results = [];
$("#search").on("keydown", "#searchinput", function(event) {
if (event.key === "Enter") {
var searchParameter = encodeURIComponent(this.value);
var link = "https://en.wikipedia.org/w/api.php?action=opensearch&search=" + searchParameter + "&limit=10&namespace=0&format=json&origin=*";
$.getJSON(link, function(data) {
for (var key in data) {
results.push(data[key]);
}
for (var i = 0; i < results.length; i++) {
for (var j = 0; j < results[i].length; j++) {
$("#results").append(results[i][j]);
}
}
})
}
});
Thanks in advance for any assistance you can provide! I am happy to provide more information if necessary.

The call to $.getJSON should be in the if block with the variable assignments.
var results = [];
$("#search").on("keydown", "#searchinput", function(event) {
if (event.key === "Enter") {
var searchParameter = encodeURIComponent(this.value);
var link = "https://en.wikipedia.org/w/api.php?action=opensearch&search=" + searchParameter + "&limit=10&namespace=0&format=json&origin=*";
$.getJSON(link, function(data) {
for (var key in data) {
results.push(data[key]);
}
for (var i = 0; i < results.length; i++) {
for (var j = 0; j < results[i].length; j++) {
$("#results").append(results[i][j]);
}
}
})
}
});
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.11.1/jquery.min.js"></script>
<div id="search">
<input id="searchinput" type="text">
</div>
<div id="results">
</div>

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);
}
}

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

question number reordering

I have a list of question in my javascript file. Each question has a question number and question description and options. A question can be added anywhere in the list of questions. So if a question is added into the top of all questions, then i need to change the question numbers of all the below ones. How can achieve this. Can i use javascript for this?

I would suggest using an <ol> for each question, and let the page handle reflowing the numbers.
Otherwise you'll need to set a target number before inserting, and for each element in the list you'll check to see if it's number is greater than the target, and then if so increment the number by one.
var Target = //new number that I want the inserted question to be
foreach (element in list) {
if (element.Number > Target) element.Number += 1;
}
list.add( //new question with # set to Target );

This works.
<ol id="questions_list"></ol>
var questions = ["A foo walks into a bar. What happens?", "Why did foo cross the road?"];
addQuestion("foo", 1);
function addQuestion(question, position)
{
if(position > 0 && position < questions.length)
{
var firstHalf = questions.slice(0, position);
var secondHalf = questions.slice(position, questions.length);
firstHalf.push(question);
questions = firstHalf.concat(secondHalf);
console.log("slice");
}else if(position <= 0)
{
questions.unshift(question);
console.log("beginning");
}else if(position >= questions.length)
{
questions.push(question);
console.log("end");
}
updateQuestionList();
}
function updateQuestionList()
{
var questions_list = document.getElementById("questions_list");
questions_list.innerHTML = "";
for(var i=0;i<questions.length;i++)
{
var question = document.createElement("LI");
question.innerHTML = questions[i];
questions_list.appendChild(question);
}
}
http://jsfiddle.net/jPxwW/1/

Array prototype ( fun! =) ):
// zero-based insert
Array.prototype.insert = function(index, item) {
var i = 0, list = [];
if (this.length == index) {
list = this;
list.push(item);
return list;
}
for(; i < this.length; i++) {
if (index == list.length) {
list.push(item);
i--;
} else {
list.push(this[i]);
}
}
return list;
};
Array.prototype.print = function (base) {
base = base || 1;
for (var i = 0, out = []; i < this.length; i++) {
out.push((base + i) + '. ' + this[i]);
}
return out.join("\n");
};
list = ['when?', 'where?', 'why?'];
list = list.insert(0, 'who?'); // first: ["who?", "when?", "where?", "why?"]
list = list.insert(3, 'how?'); // 4th: ["who?", "when?", "where?", "how?", "why?"]
list = list.insert(list.length, 'last?'); // last: ["who?", "when?", "where?", "how?", "why?", "last?"];
list.print();
/**
"1. who?
2. when?
3. where?
4. how?
5. why?
6. last?"
**/

You could do something like this using ordered lists (ol) and jQuery:
<html>
<head>
<script src="http://code.jquery.com/jquery-1.4.4.min.js" type="text/javascript"></script>
<script type ="text/javascript">
$(function(){
var n = 2;
$('button').delegate('click', function(){
$(this).parents('li').after('<li><p><span>Question'+n+'</span><button>Create new question</button></p></li>');
n += 1;
})
})
</script>
</head>
<body>
<ol>
<li>
<p><span>Question 1</span><button>Create new question</button></p>
</li>
</ol>
</body>
</html>