push pop shift unshift

• unshift/push - add an element to the beginning/end of an array
• shift/pop - remove and return the first/last element of and array

A simple diagram...

   unshift -> array <- push
   shift   <- array -> pop

and chart:

          add  remove  start  end
   push    X                   X
    pop           X            X
unshift    X             X
  shift           X      X

Check out the MDN Array documentation. Virtually every language that has the ability to push/pop elements from an array will also have the ability to unshift/shift (sometimes called push_front/pop_front) elements, you should never have to implement these yourself.