shift removes the first object in an array, and shifts all objects up in the array.

The object which was removed is then returned.

In your example, the object must be a function which itself is then invoked.

This is shorthand for:

var removedFunc = queue.shift();
removedFunc();

See MDN documentation for more info on shift:

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/shift

The shift() method removes the first element from an array and returns that element. This method changes the length of the array.

Example (Demo):

var a = [];

a.push(function(){
 alert("a");   
});

a.push(function(){
 alert("b");   
});

a.shift()(); //alerts a
a.shift()(); //alerts b

Logically it does not work and you should reverse your loop:

for (int i = position-1; i >= 0; i--) {                
    array[i+1] = array[i];
}

Alternatively you can use

System.arraycopy(array, 0, array, 1, position);