What does (Transform)o do in c#?

I am trying to translate the floating origin script I found on the unity Wiki into javascript. I’m working on this section:

if (cameraPosition.magnitude > threshold)
        {
            Object[] objects = FindObjectsOfType(typeof(Transform));
            foreach(Object o in objects)
            {
                Transform t = (Transform)o;
                if (t.parent == null)
                {
                    t.position -= cameraPosition;
                }
            }

And so far I have:

	if (cameraPosition.magnitude > 10){
		var index;
		var objectsToTransform = GameObject.FindObjectsOfTypeAll;
		for (index = 0; index < objectsToTransform.length; ++index){
			//var t = (Transform)objectsToTransform[index];
		}

But the commented out line is giving me a compiler error. What does (Tranform)o do, and how would I rewrite this for JavaScript?

Even though you have got the solution, for information I have posted this answer. That is an explicit cast in c#. It is used to convert from one data type to another. It is commonly used for converting from base to derived classes, and for converting primitive types also. For example, float x = 7.37f; int y = (int)x will give y as 7 and not raise an error (in c#).

Turns out it’s a typecast, as I had suspected, but here’s how to replicate this code in JavaScript:

var t : Transform = o;