function adjacentElementsProduct(nums) {
    if (!nums.length) {
        throw 'input array must not be empty';
        return;
    }
    
    if (nums.length === 1) {
        throw 'input array must have at least two elements';
        return;
    }
    
    let maxProduct = nums[0] * nums[1];
    for (let i = 0; i < nums.length - 1; i++) {
        if (nums[i] * nums[i + 1] > maxProduct) {
            maxProduct = nums[i] * nums[i + 1];
        }    
    }
    
    return maxProduct;
}



/**
* Test Suite 
*/
describe('adjacentElementsProduct()', () => {
    it('returns largest product of adjacent values', () => {
        // arrange
        const nums = [3, 6, -2, -5, 7, 3];
        
        // act
        const result = adjacentElementsProduct(nums);

        // log
        console.log("result: ", result);
        
        // assert
        expect(result).toBe(21);
    });
});