The reason for this is that the callback function inside setTimeout is in a different lexical environment. This is why in ES6+ functions can be defined using =>. This is so that the code within a function shares the same scope as the function.

To fix this, you can either use ES6+ syntax, where instead of function(a,b,args){...} you would use (a,b,args) => {...}:

setTimeout(() => {
  this.http.post(...);
});

or with ES5 syntax:

var root = this;

setTimeout(function(){
    root.http.post(...);
});

Hope this helps!