NAZIMUDHEEN267

1.
// !! double exclamation it returns boolean value true/false
  const array = [0, 1, 2, 3, 0];

  array.filter(num => num > 0); // bad
  array.filter(num => !!num); // good

2.
// It checks first condition is true or not then only move on to the second condition, if both condition is fullfilling then 
// the object spread operator to the parent object

NAZIMUDHEEN267

function runningSum(nums: number[]): number[] {
	let sum = [nums[0]];
	for(let i=1; i<nums.length; i++) {
		sum[i] = sum[i-1] + nums[i];
	}
	
	return sum;
}

runningSum([1,2,3,4,5,6,7,8,9,10) // return [1, 3, 6, 10, 15, 21, 28, 36, 45, 55];