Is it possible to change the value of the function parameter?

You cannot pass explicitly by reference in JavaScript; however if b were an object, and in your function you modified b‘s property, the change will be reflected in the calling scope.

If you need to do this with primitives you need to return the new value:

function increaseB(b) {
  // Or in one line, return b + 1;
  var c = b + 1;
  return c;
}

var b = 3;
console.log('Original:', b);
b = increaseB(b); // 4
console.log('Modified:', b);