JavaScript is client-side script language. Your defined variables, objects, functions etc. stored in user’s browser. When you refresh the page, it will refresh everything.
Look here for more details about JavaScript What is JavaScript? – Learn Web Development | MDN
If you want data that will not change when you refresh the page, you need to work with Server Side Languages like PHP, ASP .Net or Server Side Frameworks for JavaScript like Node.JS. Also you can store your datas in .txt files or .json files, after you can define this datas with AJAX, XMLHttpRequest, Fetch with JavaScript. But file management will expensive than other choices.
solved i need a js decimel countdown which will not reset after browser refresh