Understanding findIndex in Javascript / Typescript

Question

I am working on a piece of JS code. In a tutorial I found a piece of code I don't understand:

const position = this.quotes.findIndex((quoteEl: Quote) => {
  return quoteEl.id == quote.id;
});

I think the person who wrote the code stuffed a lot of different pieces into this line. Can somebody help me bring that into a more "easy to understand" form?

For example, the argument of the findIndex method can probably written in a separate function, right?

Thanks, Benjamin

Answer 1

findIndex calls the passed function with each element of the array and returns the index of the first element that returned true, or -1 if none did.

This is your callback function

(quoteEl: Quote) => {
  return quoteEl.id == quote.id;
}