const arrayPreviousLess = (nums) =>
    nums.map((val, ind, arr) =>
        (prev = arr.slice(0, ind).reverse()).length && (less = prev.find(item => item < val)) ? less : -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]);
    });
});