function arrayMaximalAdjacentDifference(nums) {
    //  write code here.
    let newArray = [];
    let diff = 0;
    
    // filter out the null value
    function numbersOnly(value) {
        if (typeof (value) === 'number') {
            return value;
        }
    }
    
    for (let i = 0; i < nums.length; i++) {
        diff = Math.abs(nums[i] - nums[i+1]);
        newArray.push(diff);
    }
    
    return newArray.filter(numbersOnly).reduce((a, b) => Math.max(a, b));
}



/**
* Test Suite 
*/
describe('arrayMaximalAdjacentDifference()', () => {
    it('returns largest difference between adjacent values', () => {
        // arrange
        const nums = [2, 4, 1, 0];
        
        // act
        const result = arrayMaximalAdjacentDifference(nums);

        // log
        console.log("result 1: ", result);
        
        // assert
        expect(result).toBe(3);
    });

    it('returns largest difference between adjacent values example 2', () => {
        // arrange
        const nums = [2, 9, 1, 0];
        
        // act
        const result = arrayMaximalAdjacentDifference(nums);

        // log
        console.log("result 2: ", result);
        
        // assert
        expect(result).toBe(8);
    });
});