How To Write in Javascript

How do change the syntax of this to match Javascript?

function IntNoise(32-bit integer: x)			 
    x = (x<<13) ^ x;
    return ( 1.0 - ( (x * (x * x * 15731 + 789221) + 1376312589) & 7fffffff) / 1073741824.0);    
  end IntNoise function

I think maybe this would be it, but that assumes that all the data types do what I expect them to (Javascript has weird data types, they sometimes mutate unexpectedly). At the very least it should compile. Give it a shot!

function IntNoise(x : int) : float
{
    x = (x << 13) ^ x;
    return (1.0 - ((x * (x * x * 15731 + 789221) + 1376312589) & 0x7fffffff) / 1073741824.0);
}