And I want to know If Node.js can run on FireFox ,then how?
You are mixing up JS Engine and browser.
Node.js is based on V8, which you confuse with Google Chrome. They use the same JS Engine, but you don't need any part of Chrome itself to use Node.js.
There has been project to port node.js to SpiderMonkey, but the more promising one is JXcore, a node.js fork that is JS Engine independent, and can use V8 or SpiderMonkey directly.
You also may be interested to know that Microsoft is currently porting node.js to Chakra.