function arrayPreviousLess(nums) {
    // Look at previous element index:
    // If previous element is lower number than current element return -1
    // If previous element ISN'T lower number than current, return previous element
    return nums.map((element, index) => {
        if(element > nums[index-1]){
           return nums[index-1]
        } 
        return -1
    })
}



/**
* Test Suite 
*/
describe('arrayPreviousLess()', () => {
    it('shift previous postions from the left to a smaller value or store -1', () => {
        // arrange
        const nums = [3, 5, 2, 4, 5];
        
        // act
        const result = arrayPreviousLess(nums);

        // log
        console.log("result: ", result);
        
        // assert
        expect(result).toEqual([-1, 3, -1, 2, 4]);
    });
});