Which of the following is a correct signature for a trackBy function used in ngFor?

easy📝 Conceptual Q2 of 15

Angular - Performance Optimization

Which of the following is a correct signature for a trackBy function used in ngFor?

A(item: any, index: number) => string

B(item: any) => void

C(index: number, item: any) => any

D(index: string, item: any) => boolean

Step-by-Step Solution

Solution:

Step 1: Recall the trackBy function signature
The trackBy function receives the index (number) and the item (any type) and returns a unique identifier.
Step 2: Match the correct parameter types and return type
(index: number, item: any) => any matches the signature: it takes (index: number, item: any) and returns any unique value.
Final Answer:
(index: number, item: any) => any -> Option C
Quick Check:
trackBy signature = (number, any) => any [OK]

Quick Trick: trackBy function takes index and item, returns unique id [OK]

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