How to access array item by property value and then update it's value?

I have an array of object that looks like this:

const tickets = 
[
  {
    ticketId: 'aaa',
    authorId: 'abc',
    replyCount: 0,
    status: 'Open',
    threads: [
      {
        threadId: 'abc',
        authorId: 'abc',
        direction: 'in',
        content: 'blah blah blahh'
      },
    ],
  },
  {
    ticketId: 'bbb',
    authorId: 'efg',
    replyCount: 0,
    status: 'Open',
    threads: [
      {
        threadId: 'efg',
        authorId: 'efg',
        direction: 'in',
        content: 'blah blah blahh'
      },
    ],
  },
  .......
]

Now I want to access the array item where ticketId equals aaa and change it’s threads property.

I have tried doing using tickets['aaa'].threads = [ ... ] but it throws these errors:

Eslint: Unsafe member access .threads on an 'any' value

TypeScript: Element implicitly has an 'any' type because index expression is not of type 'number'

>Solution :

Find the index where ticketId equals "aaa"

tickets[tickets.findIndex(v => v.ticketId === "aaa")].threads = [/* ... */];

With index validation:

const idx = tickets.findIndex(v => v.ticketId === "aaa");
if (idx > -1) tickets[idx].threads = [/* ... */];