how to test if the mouse is being clicked unity code example

Example 1: how to detect a mouse click in unity

using UnityEngine;
using System.Collections;

		if (Input.GetMouseButtonDown(0)) {
        	//Left Mouse Button
        } else if (Input.GetMouseButtonDown(1)) {
        	//Right Mouse Button
        } if (Input.GetMouseButtonDown(2)) {
        	//Middle Mouse Button
        }

Example 2: unity Check if mouse clicked UI element

EventSystem.current.IsPointerOverGameObject()