Question

var data = {};


....

data[someprop][someotherprop] = 'bla bla'

I get

Uncaught TypeError: Cannot read property ... of undefined and Cannot set property of...

Yes, the object doesn’t have these properties ..yet, but I’m setting them in that line where I get the error lol. So what’s up with that?

Answer 1

if someprop and someotherprop are variables, Richard D’s answer is correct, if they are hardcoded strings, you could write your code like this:

var data = {someprop:{someotherprop: 'value'}};

if, however, they are values stored in variables, and you really – really want to cram everything into a single line, try something like this:

var data = {window.someprop : {window.someotherprop: 'value'}};

where window can be replaced by any object, if the someprop value is itself a property of an object:

var data = {someForm.name : { formElement.name : formElement.value}};

Or jQuery objects, since your tag suggest you’re using jQuery:

var data= {$('#formId').attr('name'):{$('#formSelect').attr('name'): $('#formSelect').val()}};

Note: the jQuery example is not to be recommended, as the id selector is used twice on the same element. jQuery will scan the DOM-tree twice, so you’re better of storing your that #formSelect element in a variable somewhere.