A function has a fixed point when for some value of x, x = f(x). This is interesting because it's some change, that doesn't change the result.

in the lingua franca of javascript.

  var timesThree = (x => x * 3)
  //for this function 0 is a fixed point...
  var a = 0
  console.log(a == timesThree(a))
  //7 is not a fixed point
  var b = 7
  console.log(b == timesThree(b))