function arrayPreviousLess(nums) {
    //  write code here.
    let a =[]
    for(let i=0; i<nums.length; i++) {
        if(nums[i - 1] < nums[i]) {
            a.push(nums[i -1])
        }  
        else {
            a.push(-1)
        }
    }
    return a
}



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