Follow along yourself in the Chrome Console.
Arrays are 'zero' based so the first slot is a, then a etc. If there are N slots then the last slot is a[N-1]
'push' a number onto the end of an array. Increases array length.
'pop' a number from the end of an array. Alters array length.
'shift' a number from the beginning of an array. Alters array length.
'unshift' adds a number from the beginning of an array. Alters array length.
'sort' - sorts an array.
'reverse' - reverse sorts an array.
'indexOf' returns the index location of a number.
Concatenate 2 arrays into a single array.
'slice' a section out of the array - leaves the array the same.
'splice' a section out of the array - mutilates the array.
It is often used to remove the first element. The array can then act like a 'queue' ie splice(0,1)
'splice' can also 'repair' an array by inserting elements.
splice(start_pos, 0, elements_to_be_inserted);