const byTwo = a => {
    const r = []
    for(let i = 0; i < a.length; i++){
        if(i < a.length - 1 ){
            r.push([a[i], a[i + 1]])
        }
    }
    return r
}


const arrayMaximalAdjacentDifference = nums => Math.max(...nums.map((c, i, a) => a[i+1] && [c, a[i+1]]).filter(e => Array.isArray(e)).map(a => Math.abs(a[0] - a[1])))



/**
* 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);
    });
});