Javascript: Add key/value pairs in nested dict; key and value are variables

Question

I have a dictionary of the following structure:

myDict = {key1:{innerKey1:innerValue1, innerKey2:innerValue2}, key2:{},...}

Based on: How can I add a key/value pair to a JavaScript object?

I tried to add inner key/value pairs like this:

someArray=['foo','bar']
var identifier = someArray[0]
var info = someArray[1]
myDict[key1][identifier] = info;

Or like this:

myDict[key1].identifier = info;

But I get the error 'cannot set property of undefined'. I think this is due to the identifier not being defined in myDict yet, but I cannot figure out how to achieve this:

myDict = {key1:{innerkey1:innerValue1, innerKey2: innerValue2, foo:bar,...}, key2:{},...}

Please note: I know in this example the assignment of variables is not necessary. I need to figure out the concept for a bigger, more complex project and this is the minimum "non-working" example.

Thanks in advance :)

score 4 · Accepted Answer · answered Aug 09 '19 at 09:27

From your snippet, key1 doesn't seem to be defined.

You also want to make sure that the object is defined before trying to access it

someArray=['foo','bar']
var identifier = someArray[0]
var info = someArray[1]
if (!myDict[key1]) myDict[key1] = {};
myDict[key1][identifier] = info;

Jack Bashford · Answer 2 · 2019-08-09T09:29:42.913

3

Bracket notation requires the key be a string:

myDict["key1"][identifier] = info;

Or just use dot notation:

myDict.key1[identifier] = info;

edited Aug 09 '19 at 09:29

answered Aug 09 '19 at 09:25

Jack Bashford

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This would have been my answer too, not sure why someone thought it was bad. – Ozgar Aug 09 '19 at 09:27
1

key1 is probably a variable to be fair. – Morphyish Aug 09 '19 at 09:27
I know @Morphyish, but the fact that they have not defined it has caused the error. – Jack Bashford Aug 09 '19 at 09:28
1

Since identifier is a variable defined above `myDict.key1[identifier] = info` would be the correct solution – BJRINT Aug 09 '19 at 09:28
Fixed @BJRINT, any better? – Jack Bashford Aug 09 '19 at 09:29
1

@JackBashford my own bet is on the fact that `key1` has no associated value in the dict when they are trying to update its property ;D – Morphyish Aug 09 '19 at 09:31

Javascript: Add key/value pairs in nested dict; key and value are variables

2 Answers2