Referencing sp.js in html page gives error

Question

I have referenced sp.js in html page in my sp hosted add-in, in order to use client object model in javascript. But it's giving me an error on _spPageContextInfo while it's referencing the sp.js, why sp.js is referencing _spPageContextInfo?

In the chrome error message it says:

Uncaught Sys.InvalidOperationException: Sys.InvalidOperationException: Cannot find current web URL information on the page.

Here's a screenshot of the error:

Error message taken from sp.js, and it gives an error when referencing new SP.ClientContext()

Answer 1

I give you a example where you can view what are the files you need to use sp.js http://todosharepoint.blogspot.com.ar/2014/08/que-librerias-necesitamos-para-poder.html