Cannot create property on string

Question

I have stumbled on a weird issue when trying to recursively set properties on an empty object with the following code:

Simplified code

const birthdays = {};

// Loop -> Passing day, id and birthday
birthdays[day] = day;
birthdays[day][id] = birthday;

Example of day: '01012017'

Example of id: 1547

Example of birthday: {name: John}

Error message

Cannot create property '123' on string '06012017'

I saw some people with Angular having this issue but their answer don't solve anything for me (as is angular specific syntax etc).

Answer 1

Empty Objects need to be individually created before their values are assigned. And use of const is not a good idea here, anyway, it's just my suggestion.

const birthdays = {};
var day = 123;
var id = 21;
var birthday = 2016;
// Loop -> Passing day, id and birthday
birthdays[day] = {};
birthdays[day][id] = birthday;

Answer 2

I had a similar error message TypeError: Cannot create property 'false' on boolean 'false' in Node 14.3.0 (ES 2019), using the new Javascript semicolon-less syntax, with a variable declaration and assignment followed by a destructuring assignment on the next line.

The code that caused the error:

var a = b ()
[c, d] = e ()

Solved by:

var a = b ()
;
[c, d] = e ()