why do typhoon and hurricane affects eastern coast whereas western coast remains undisturbed?
Hurricanes and typhoons are the same type of weather event, occurring in different areas.
Depending on its location and strength, a tropical cyclone is referred to by names such as hurricane, typhoon, tropical storm, cyclonic storm, tropical depression, and simply cyclone.
A typhoon is a tropical cyclone which occurs in the Pacific Ocean, west of 180 degrees West Longitude. The same type of storm, located in the eastern Pacific or off the Atlantic Ocean, is called a hurricane. There have been significant storms of these types along both the eastern and western coasts of North America, as well as in other parts of the world. Consider Hurricane Katrina (southern United States), Hurricane Pauline (western Mexico), and Typhoon Morakot (Taiwan).
The direction in which any of these storms travels is affected by the prevailing trade winds in the area of the storm. These winds combine with the rotation of the Earth to affect exactly where the impact of any particular storm is felt.