Topic Description

Implement a findIndex function from scratch. It should accept three parameters:

• array: The array to search.
• predicate: A test function used to determine if an element meets the required condition.
• fromIndex: The starting index for the search. If not specified, the default is 0.

The findIndex function should return the index of the first element in the array that satisfies the predicate function. If no elements satisfy the condition, it should return -1.

// Examples
console.log(findIndex([1, 13, 7, 54], (num) => num > 10)); // 1
console.log(findIndex([1, 13, 7, 54], (num) => num > 200)); // -1

Answer

function findIndex(array, predicate, fromIndex=0){
	let resultIndex = -1 
	if(array.length ==0){
		return resultIndex
	}
	const startIndex = fromIndex < 0 ? fromIndex + array.length : fromIndex
	for(let i = startIndex; i < array.length; i++){
		if( predicate(array[i]) ){
			resultIndex = i
			break
		}
	}
	
	return resultIndex
}