Develop Reference

why doesn't this return an l-value?

Maybe ReSharper or visual studio is wrong, but I don't think that this returns an r-value. I also don't think it actually sets the property in the $parent controller:
function getParentItem(path) {
var obj = $scope.$parent;
var param = null;
var items = path.split(".");
for (var i = 0; i < items.length; i++) {
var item = items[i];
var split = item.split("(");
if (split.length === 2) {
param = split[1].replace(/[\)\']/g, "");
}
obj = obj[split[0]];
}
if (param == null) {
var thisObj = obj;
return thisObj;
} else {
return { obj: obj, param: param };
}
}
If I do this:
getParentItem($scope.someProperty) = "yadda"
I get error marked by probably ReSharper and I think it doesn't actually set the new value

As Amy/Volkan said your code is not valid but I think I get what you want to do. There are lots of ifs but here it goes:
if your $scope.someProperty is string property that you want to reassign on result of the function getParentItem, and your function returns object that can have that param ($scope.someProperty), first you need to figure out which path you pass in but it looks like it's some string separated by dots.
// so then assign result of the function to some variable
// you need to pass somePath to function
let parentItem = getParentItem(somePath);
// then change that property
parentItem[$scope.someProperty] = "yadda";
or another possibility what you might need would be:
parentItem.param[$scope.someProperty] = "yadda";
then do whatever you want with parentItem like put it on $scope or whatever.
If you want better help please do some jsfiddle or something.

The problem is (and I slap my head on how stupid I was) that the leaf branches of this $scope object aren't objects themselves, and in some cases in our code they don't even exist yet. You get so used to $scope being an object you fail to realize that the final elements can't possibly be objects at least in Javascript.
So the solution was to pass the value that I wanted to set as a parameter:
function getParentItem(path, optionalValue)
On the final loop of the parent search, if optionalValue is passed, I can then set the value onto the object:
obj[--last parameter name--] = optionalValue;

Check if nested object is declared and has a value without so many conditional checks

I have a JSON object which I get from a server. The key which I get the value from looks something like this:
var myJson = data.body.region.store.customer.name;
I am trying to get the name key here, but sometimes the JSON (which comes from a service I have no control over) will have some empty fields, like for instance name might not be defined so the object will actually look like this: data.body.region.store.customer. Sometimes too customer, or store, or region might not be defined (If the data doesn't exist the service doesn't return a null or empty string for the value).
So if I need the name what I am doing is this:
if(data.body.region.store.customer.name){
//Do something with the name
}
But say even store isn't defined, it will not get the value for name(which I would expect to be undefined since it doesn't exist) and the program crashes. So what I am doing now is checking every part of the JSON before I get the value with AND operands:
if(data && data.body && data.body.region && data.body.region.store && data.body.region.store.customer && data.body.region.store.customer.name){
//Do something with the name value then
}
This works, because it checks sequentially, so it first checks does data exist and if it does it checks next if data.body exists and so on. This is a lot of conditions to check every time, especially since I use the service a lot for many other things and they need their own conditions too. So to just check if the name exists I need to execute 6 conditions which of course doesn't seem very good performance wise (and overall coding wise). I was wondering if there is a simpler way to do this?

var myJson = null;
try {
myJson = data.body.region.store.customer.name;
}
catch(err) {
//display error message
}

You can try following
function test(obj, prop) {
var parts = prop.split('.');
for(var i = 0, l = parts.length; i < l; i++) {
var part = parts[i];
if(obj !== null && typeof obj === "object" && part in obj) {
obj = obj[part];
}
else {
return false;
}
}
return true;
}
test(myJson, 'data.body.region.store.customer.name');

isNaN not working JavaScript

I’m having trouble with the isNaN function is JavaScript. I have a variable, trc, which I know is not a number, but I want my code to be able to tell. Unfortunately, isNaN isn’t detecting that it’s not a number, yet when I use an alert to show the value of the variable, it is indeed not a number.
trc = parseInt(getCookie("trc"));
cnn = parseInt(getCookie("cnn"));
klove = parseInt(getCookie("klove"));
if (isNaN(trc)) {
trc = 0;
}
if (getCookie("trc") == undefined) {
trc = 0;
} else {
trc = parseInt(getCookie("trc"));
}
alert(trc);
BTW, I have a separate function, getCookie(), that I made myself to get the value of a cookie.

You should check value of trc before.
If trc is null, then isNaN(null) return false.
Edit:
parseInt method doesn't return null value, but trc can be modified by external code - therefore I recommend using namespaces e.g:
var namespace = namespace || {};
namespace.trc = .....

JavaScript throws TypeError saying that my variable is undefined

I don't have much experience in JavaScript, so far I have this:
function loop() {
var authorDivs = document.getElementById('ctl00_MainContent_MCPObjectInfo_dvCreatorView').getElementsByTagName("div");
for (var i = 0; i < authorDivs.length; i++) {
var divOfDiv = authorDivs[i].getElementsByTagName("div");
if (typeof divOfDiv.item(i) === 'undefined' || divOfDiv.item(i) === null) {
console.log("This is undefined or null");
}
else {
var realDivs = divOfDiv.item(i);
realDivs.item(i).textContent = "please work plz";
}
}
}
I get the following error from the console in FireFox: TypeError: realDivs is undefined on this line: realDivs.item(i).innerHTML = "please work plz";
Essentially what I have (in my mind) is a loop that goes through authorDivs and gets all of the divs within those divs and saves them in divOfDiv. I then check to see if the divs in divOfDiv are undefined or null, if they are not then those divs get saved in a variable realDivs which I then use to edit the innerHTML. That's what I'd ideally like to see happen, what is causing the error? What am I doing wrong?
Note: I do not have access to jQuery but only JavaScript.
Edit: I've added the changes suggested below and its fixed that -- thanks! But I'm now getting the following error: TypeError: realDivs.item is not a function
What is causing that? And on another note how do I know when I'm dealing with an array and when I'm dealing with an HTMLCollection? Do you just assume? I've never used a loosely typed language before so its new to me.

Well, you'll need to move that code inside the conditional block that is supposed to prevent it! Also, || "null" is not going to work as you expect, you'll need to check for || divOfDiv.item(i) === null explicitly.
So try
for (var i = 0; i < authorDivs.length; i++) {
var divOfDiv = authorDivs[i].getElementsByTagName("div");
if (divOfDiv.item(i) == null) {
console.log("This is undefined or null");
} else {
var realDivs = divOfDiv.item(i)
realDivs.item(i).innerHTML = "please work plz";
console.log(divOfDiv.item(i));
}
}
However, that still doesn't really work for two reasons:
The i index you use to access the i-th divOfDiv comes from the iteration over authorDivs - hardly what you want. Instead, use a second loop over all divOfDivs.
Your realDivs variable does hold a single <div>, which does not have an .item method. You'd just directly access its .innerHTML property.
So you should use
var authorDivs = document.getElementById('authorView').getElementsByTagName("div");
for (var i=0; i<authorDivs.length; i++) {
var divsOfDiv = authorDivs.item(i).getElementsByTagName("div");
for (var j=0; j<divsOfDiv.length; j++) {
var realDiv = divsOfDiv.item(j);
realDiv.innerHTML = "please work plz";
console.log(realDiv);
}
}

it will happen in case when your if (typeof divOfDiv.item(i) === 'undefined' || 'null') returns true. Then you never initialize realDivs (what would happen if condition was falsy). Later you try to call item function on that unitialized object

There are two problems in the code.
comparing DOM object with 'undefined' and null. If div tag is not available in authorDivs[i], it will return empty DOM array. So, comparision of empty DOM array with undefined and null is not good approach. We can use array length property for doing validation.
divOfDiv = authorDivs[i].getElementsByTagName("div");
if(divOfDiv.length > 0) { console statement}
As item(i) is already return single DOM element, item(i) of "realDivs" variable is not proper approach. In addition to this, innerHTML method needs to be used after validating whether realDivs contains DOM element. Please update the code as below.
var realDivs = divOfDiv.item(i);
realDivs ? (realDivs.innerHTML = "please work plz"): null;
Note : item(i) will return null if DOM is not available.

Is there a way to prevent undefined javascript variables from displaying 'undefined' when inserted into html?

I am appending text which is stored in a javascript variable into a div element. The issue is that the depending on the situation there may or may not be text stored in that variable. If there is not I end up with the text 'undefined' where the valid text would have been in the div.
so as an example:
htmlelement.innerhtml = '<h2>'+array.object.title+
'</h2><p>'+array.object.textField1+
'</p><p>'+array.object.textField2+
'</p><p>'+array.object.textfield3+'</p>';
This shows up in a function which will run for each object in the array. Not all of the objects have content in all 3 text fields.
So is there an easy way to prevent 'undefined from being printed?
Right now I have this before the previous line:
if (!array.object.textfield1) {
array.object.textfield1 = ' ';
}
if (!array.object.textfield2) {
array.object.textfield2 = ' ';
}
if (!array.object.textfield3) {
array.object.textfield3 = ' ';
}
But this is not a practical solution if there are a lot of variables that need to be checked.

Can you use the logical operator || ?
array.object.textField1||''
Note: Please do take care of values like 0 or any other falsy values .

Use "The New Idiot" answer this is here just fro an extra method.
The other answer is better because it molds the check into the logic ( a good thing!) and is better for performance.
with that said REGEX!!
htmlelement.innerText = htmlelement.innerText.replace('undefined', '');

check each array item to see if its undefined with the **typeof** operator.
for each array item if the **typeof** is **undefined** you can do eather 2 things:
1. set to default
2. remove with splice()
example:
function cleanArray(theArray){
for(i=0;i < theArray.length;i++){
if(typeof theArray[i] == "undefined"){
theArray[i]="";//OR SPLICE IT OU WITH splice()
}
}
}
//NOW CALL THIS FUNCTION EVERYTIME PASSING IT THE ARRAY
cleanArray(arrayOfItems);
no simple way around this, you need to plan your design accordingly

"The New Idiot" answer is pretty good if you only have a few. If you have a more complicated object that you want to sort out, one option would be to iterate over the properties and set them to an empty string if they are undefined. e.g.
var o = {
t1: undefined,
t2: "hey"
};
for (prop in o) {
if (o.hasOwnProperty(prop) && typeof o[prop] === "undefined") {
o[prop] = "";
}
}
jsFiddle: http://jsfiddle.net/Ca6xn/