I think this is not offtopic -- if I understand the question correctly, the question asks for a LaTeX editor that has real-time rendering. This is very much on topic and would make it a duplicate of our multiple questions about real-time preview. To the OP: I recommend using an online editor like ShareLaTeX or Overleaf, as recommended by this answer.
– ShreevatsaRJun 15 '17 at 19:25
mathjax. It is a javascript library to render a subset of latex syntax in web pages. – Guido May 17 '17 at 02:42