Given an array arr of numbers, return the count of elements that are even integers (divisible by 2). The value 0 counts as even.
Examples
Input: arr = [1, 2, 3, 4]
Output: 2
Input: arr = [-2, -5, -8]
Output: 2
Input: arr = [0, 2, 3]
Output: 2
Input: arr = []
Output: 0
Constraints
- Input must be an array of finite numbers
- Count only numbers that are integers and divisible by 2
- Return false for non-array inputs
- Return false for arrays containing non-number values
- Return false forarrays containing NaN, Infinity, or -Infinity
Function Signature
function countEvens(arr) {
// Your code here
}
Test Cases
- Base cases: empty array [], single even [ 2 ], single odd [ 1 ]
- Mixed arrays: [ 1, 2, 3, 4 ], [ -5, 2, -3, 4 ]
- All evens: [ 2, 4, 6 ]
- No evens: [ 1, 3, 5 ]
- Zeros: [ 0 ], [ 0, 0, 0 ]
- Decimals: treat only integer values as even (e.g., 2.0 is even, 2.2 is not)
- Invalid inputs: null, undefined, 42, '8', {}, () => {}, [1, 'a'], [NaN], [Infinity]
