Sorting a List of Custom Objects with Nested Properties in TypeScript - Encountering Undefined Behavior
I'm upgrading from an older version and I am trying to sort an array of custom objects in TypeScript based on a nested property, but I am encountering unexpected sorting behavior. The objects have a structure like this: ```typescript interface Item { id: number; name: string; details: { category: string; price: number; }; } const items: Item[] = [ { id: 1, name: 'Item A', details: { category: 'B', price: 20 } }, { id: 2, name: 'Item B', details: { category: 'A', price: 15 } }, { id: 3, name: 'Item C', details: { category: 'B', price: 25 } }, { id: 4, name: 'Item D', details: { category: 'A', price: 10 } } ]; ``` I want to sort the `items` array first by `details.category` alphabetically and then by `details.price` numerically in ascending order. I wrote the following comparator function: ```typescript const compareItems = (a: Item, b: Item): number => { if (a.details.category < b.details.category) return -1; if (a.details.category > b.details.category) return 1; return a.details.price - b.details.price; }; ``` Then, I attempted to sort the items with: ```typescript items.sort(compareItems); ``` However, I'm getting unexpected results where the items are not sorted correctly by category. The `console.log(items);` after sorting shows: ``` [ { id: 2, name: 'Item B', details: { category: 'A', price: 15 } }, { id: 4, name: 'Item D', details: { category: 'A', price: 10 } }, { id: 1, name: 'Item A', details: { category: 'B', price: 20 } }, { id: 3, name: 'Item C', details: { category: 'B', price: 25 } } ] ``` As you can see, the items with category 'A' are sorted properly, but those with category 'B' are not in the expected order based on their price. It seems that the sort is not stable, especially when there are equal categories. I've tried adding logging inside the comparator function to inspect the values being compared, and they look correct, so I am unsure why the sort isn't behaving as expected. Is there something I am missing in my comparator function or TypeScript's sort implementation? I am using TypeScript version 4.5.2 and running this in a Node.js environment. Any help would be appreciated! I'd really appreciate any guidance on this. For reference, this is a production mobile app. Could someone point me to the right documentation?