I help run a bi-weekly algorithm coding guild at work where we solve many programming problems together. It’s a very fun and rewarding experience and I get exposed to many different programming languages. Sometimes, when I “shift gears” between languages, I mix up the prototype methods in javascript.

The one I recently flubbed was shift() and unshift(), which seems silly but when you’re moving fast its an honest mistake to make!

Let’s review their MDN entries

Array.prototype.shift()

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

Array.prototype.unshift()

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

How I always remember the difference:

If we literally break up the words into letters (similar to split() lol) you might notice something:

["u","n","s","h","i","f","t"]
// vs
["s","h","i","f","t"]

The way I see it, unshift is “updating” our array above, “shift” with two additional characters in the front (“u” and “n”). In my mind I also remember this by matching up the “u” of update and “u” of unshift. Shift on the other hand complements this as its missing the “u.” In fact this is even how unshift() works! It prepends characters to the front of the array.

Hope this little trick helps you! Remember we update (think “u”) with unshift… with two characters in the front of the word shift > unshift.