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JSON.parse an Undefined object from Local Storage

I am having a LocalStorage item which I am parsing into a variable like this:
let resp = JSON.parse(localStorage.getItem('someKey'));
The thing is sometimes, the localStorage may not have the value and it may return an Undefined object to parse which is resulting in following error:
SyntaxError: Unexpected token U in JSON at position 0
I have tried this:
let resp = localStorage.getItem('someKey') ? JSON.parse(localStorage.getItem('someKey')) : null;
But I believe this is not very optimal way of handling this, any suggestions are welcome

your solution is just fine, if you want it to be shorter, you could try this
let resp = JSON.parse(localStorage.getItem('someKey') || null)
Here is how it works:
localStorage.getItem('someKey') || null will evaluate the left side of the code first, if localStorage.getItem('someKey') returns undefined or '' empty string, it will return the right side code which is null
Then, JSON.parse(null) will return null instead of error

You could try something like this:
let resp = null;
const storedResp = localStorage.getItem('someKey');
if (storedResp) {
try {
resp = JSON.parse(storedResp);
} catch (e) {}
}
This shouldn't generate any errors since you're only parsing it to JSON if it exists, and then catching any errors if JSON parsing fails. You're left with resp being equal to null or the stored data as JSON, with no errors in any case.
As others have said, your current solution is fine, but there are two potential issues with it as written:
You access the item in localStorage twice, which may be unnecessarily slow if it is a large object.
Many companies prefer (or require) that you wrap lines at 80 characters and your current solution is 96 characters long.

What is a PoliglotMap in GraalVM?

I am working with the org.graalvm.polyglot script engine in my Java11 project to evaluate a JavaScript.
The script to be evaluated returns a JavaScript array with two entries.
...
var result={};
result.isValid=false;
result.errorMessage = new Array();
result.errorMessage[0]='Somehing go wrong!';
result.errorMessage[1]='Somehingelse go wrong!';
....
In my java code I try to evaluate the result object:
Value resultValue = context.getBindings(languageId).getMember("result");
In my Eclipse Debugger I can see that I receive a PolyglotMap containing the expected values:
I can iterate over that map to get the values with a code like this:
...
try {
mapResult = resultValue.as(Map.class);
} catch (ClassCastException | IllegalStateException | PolyglotException e) {
logger.warning("Unable to convert result object");
return null;
}
Iterator it = mapResult.entrySet().iterator();
while (it.hasNext()) {
Map.Entry pair = (Map.Entry) it.next();
String itemName = pair.getKey().toString();
Object itemObject = pair.getValue();
...
In this way I am able to extract the boolean 'isValid'. But with the object 'errorMessage' I struggle.
Inspecting the Object again within the Eclipse Debugger it looks like this:
If I test this object it is an instanceOf Map. But I am unable to get any of the values out of this object.
Can anybody help me to understand what exactly this object represents and how I can extract the both values 'Someting go wrong!' and 'Sometingelse go wrong!' ?
When I iterate over this second map it seems to be empty - even if the debugger shows me the correct values.

I'm not 100% sure why as(Map.class) behaves that way, it might be worth creating an issue on github to figure it out: github.com/oracle/graal
But if you access the values using the API without converting to a Map it would work as you expect:
var errorMessage = resultValue.getMember("errorMessage");
errorMessage.hasArrayElements(); // true
var _0th = errorMessage.getArrayElement(0);
var _1th = errorMessage.getArrayElement(1);
You can also convert the polyglotMap to Value and then do it:
val errorMessage = context.asValue(itemObject);
errorMessage.hasArrayElements(); // true
errorMessage.getArrayElement(0);
PolyglotMap of course has the get method. And the Value javadoc says that:
Map.class is supported if the value has Value.hasHashEntries() hash entries}, members or array elements. The returned map can be safely cast to Map. For value with members the key type is String. For value with array elements the key type is Long.
Can you try getting them with the Long keys?
There might be something obvious I'm missing, so in any case it's better to raise an issue on GitHub.

node.js change in concatenation?

I'm trying to debug some code that another programmer has left for me to maintain. I've just attempted to upgrade from node.js 5 to node.js 8 and my database queries are for some requests coming back with key not found errors
We're using couchbase for the database and our document keys are "encrypted" for security. So we may have a key that starts like this "User_myemail#gmail.com" but we encrypt it using the following method:
function _GetScrambledKey(dbKey)
{
//select encryption key based on db key content
var eKeyIndex = CalculateEncryptionKeyIndex(dbKey, eKeys.length);
var sha = CalculateSHA512(dbKey + eKeyIndex);
return sha;
}
function CalculateEncryptionKeyIndex(str, max)
{
var hashBuf = CalculateSHA1(str);
var count = 0;
for (var i = 0; i < hashBuf.length; i++)
{
count += hashBuf[i];
count = count % max;
}
return count;
}
We then query couchbase for the document with
cb.get("ECB_"+encryptedKey, opts, callback);
In node5 this worked but in node8 we're getting some documents return fine and others return as missing. I outputted the "ECB_"+encryptedKey as an int array and the results have only confused me more. They are different on node5 to node8 but only by one character right in the middle of the array.
Outputting the encryptedKey as an int array on both versions shows this
188,106,14,227,211,70,94,97,63,130,78,246,155,65,6,148,62,215,47,230,211,109,35,99,21,60,178,74,195,13,233,253,187,142,213,213,104,58,168,60,225,148,25,101,155,91,122,77,2,99,102,235,26,71,157,99,6,47,162,152,58,181,21,175
Then outputting the concatenated string, in the same way, shows slightly different results
This is the node8 output
Node8 key: 69,67,66,95,65533,106,14,65533,65533,70,94,97,63,65533,78,65533,65533,65,6,65533,62,65533,47,65533,65533,109,35,99,21,60,65533,74,65533,13,65533,65533,65533,65533,65533,65533,104,58,65533,60,65533,25,101,65533,91,122,77,2,99,102,65533,26,71,65533,99,6,47,65533,65533,58,65533,21,65533
And this is the node5 output
Node5 key: 69,67,66,95,65533,106,14,65533,65533,70,94,97,63,65533,78,65533,65533,65,6,65533,62,65533,47,65533,65533,109,35,99,21,60,65533,74,65533,13,65533,65533,65533,65533,65533,65533,104,58,65533,60,65533,65533,25,101,65533,91,122,77,2,99,102,65533,26,71,65533,99,6,47,65533,65533,58,65533,21,65533
I had to run it through a diff tool to see the difference
Comparing that to the original pre-append array it looks like the 225 has just been dropped in node8. Is 225 significant? I can't understand how that would be possible otherwise unless it's a bug. Does anyone have any ideas?

Looks like this was a change in v8 5.5 https://github.com/nodejs/node/issues/21278

A lot of the issues you are facing, including the concatenation can be cleaned up using newer features from ES6 that are available in node 8.
In general, you should avoid doing string concatenations with the + operator and should use string literals instead. In your case, you should replace the "ECB_"+encryptedKey with `ECB_${encryptedKey}`.
Additionally, if you want to output the contents of the integers values from this concatenated string, then you are better off using .join, the spread operator (...) and the Buffer class from Node as follows:
let encKey = `ECB_${encryptedKey}`;
let tmpBuff = Buffer.from(encKey);
let buffArrVals = [...tmpBuff];
console.log(buffArrVals.join(','));
Also, if you can help it, you really should avoid using var inside of function blocks like it exists in your sample code. var performs something called variable hoisting and causes the variable to become available outside the scope it was declared, which is seldom intended. From node 6+ onward the recommendation is to use let or const for variable declarations to ensure they stay scoped to the block they are declared.

Logging objects shows all properties but logging the properties individually shows 'undefined'

I'm trying to port a PHP function I built to Javascript and have been finding many differences that cause a lot of extra work. I am stuck on this one and cannot find any logic to it:
X: 95.29
Y: 27.39
testParse2.RXdec : 0.1
var curPos={};
curPos={};
console.log(curPos); //X:97.19 Y:27.39 (I expect an empty object)
console.log(curPos['X']); //undefined (seems ok but makes no sense with above)
console.log(curPos['Y']); //undefined (seems ok but makes no sense with above)
for(var Ri=0; Ri < 20; Ri++){
curPos['X'] = "";
curPos['Y'] = "";
console.log(curPos['X']); // "" (seems ok)
console.log(curPos['Y']); // "" (seems ok)
console.log(curPos); //X:97.19 Y:27.39
curPos.X = (((XY(lastPos[AV['A']], 'X')*1)+(testParse2.RXdec*1*Ri)).toFixed(10)*1);
curPos.Y = (((XY(lastPos[AV['B']], 'Y')*1)+(testParse2.RYdec*1*Ri)).toFixed(10)*1);
console.log(curPos); // X:97.19 Y:27.39 (I expect X:95.29 + 0.1 each loop Y:27.39)
console.log(curPos.X); // 95.29 (correct by why is above different?)
console.log(curPos.Y); // 27.39 (correct by why is above different?)
}
The things that confuse me the most are:
curPos gets a value before the loop even starts. The value is the
value that curPos should have after the final iteration.
during the loop the console log for curPos and curPos.X or .Y do not
contain the same values.
during the loop the console log for curPos is always the same despite changing .X and .Y each iteration
Edit: #str gave the correct explanation for the console trouble but it seems that this problem is beyond the console and actually effects the object values.
after using JSON.strigify I can see this (which is good):
console.log(JSON.stringify(testParse2));
"Xdec":97.99
"Xdec":98.09
"Xdec":98.19
but now I try to transfer the data to its final array but that final array is filled with 'lazy' values:
T['tool'][T['curTool']]['points'][lineID] = testParse2;
console.log(JSON.stringify(T));
"Xdec":98.19,"Ydec":27.39,"curX":323.19,"curY":177.39
"Xdec":98.19,"Ydec":27.39,"curX":323.19,"curY":177.39
"Xdec":98.19,"Ydec":27.39,"curX":323.19,"curY":177.39
If I stop using objects in the loop and switch to variables then build my final array like this it works:
T['tool'][T['curTool']]['points'][lineID] = {'curX' : curX,
'curY' : curY,
'TYP' : 'DR',
'lineID' : lineID,
'lineName' : lineName,};
How do you send the actual object values at a particular iteration of a loop to a different array?

Browsers evaluate objects lazily in when logging. So when you expand them after the loop, they will show the properties they have at the moment of expanding and not the ones they had when the object was logged.
You can verify that by using
console.log(JSON.stringify(curPos));
instead of
console.log(curPos);

split() is not giving the expected outcome

I'm having problems why my .split() function.
somehow when i splay my line the first [0] element in the array can be accessed but the 2nd [1] can't
I have the following string:
,{"relationID":"000001","recID":"1d2712eb-4f08-4b4f-b6e9-600c9631b503"
And the code below is how i try to split this (tempArray contains a x number of strings like the above):
var templine = tempArray[i].substr(1, tempArray[i].length);
//alert(templine);
var line = templine.split(',');
var s1 = line[0].split('"')[3];
var s2 = line[1].split('"')[3];
when i use alert(s1) or alert(s2) i do get the value however, the folowing error always occurs on the last line (var s2):
caught TypeError: Cannot read property 'split' of undefined
this causes the rest of my script to crash and it won't finish what it's supposed to, displaying an empty page.
My question, what is going wrong here? why does s1 function properly and s2 which is exactly the same except for the index of the line array crash my script.
I want to emphasise when i use the alert function to check the value of my variable s1 and s2 they do contain the right value.
EDIT:
maybe a nice bonus since there might be an easyer way.
after I've gotten the values s1 and s2 i want to put them in a map like so:
map[s2] = s1;
as you can probably tell the string i use is the result of splitting 1 humongous string on ('}'). the code displayed here is what i do when looping trough this array.

That can only be caused by a attempt to access element on the array that is really undefined. Probably your input is not what you are expecting.
Check if line.length > 1 before you try to read those indexes of the array.
As it seems to be a JSON, may be you should try to parse the JSON, it would make your code more readable and reliable. Check JSON.parse browser compatibility before using it (IE8+).
For example:
var data = JSON.parse('{ "field1": "value1", "field2": "value2" }');
var s1 = data['field1'];
var s2 = data['field2'];
Hope I've helped.