Mnemonic for shift() and unshift()?

Question

JavaScript push() and pop() are intuitive method-names because they come from the context of using an array as a "stack". You can "push" things to a stack meaning a new item is added as the new last element of the array. push() pushes a new element into the array. Pop() pops one off it.shift() and unshift() on the other hand I always had trouble with. One of them adds a new element to the front of the array and the other removes and returns the 1st element. But which is which? I can google the answer but would be nice if I didn't have to google. And worse, sometimes I got confused between the two and used shift() where unshift() should have been used => Error,, stack overflow!So I googled for "Mnemonics for shift() and unshift()", and found an entry on Stack Overflow. But that question was "Closed because the answers are opinion-based". I looked at the answers available but none of them struck me as particularly memorable.Now after years of struggling with this confusion I think I've come up with a mnemonic I can live with:Word "shift" is shorter than the word "unshift". Therefore shift() makes the array shorter.Word "unshift" is longer than the word "shift". Therefore unshift() makes the array longer.I know it doesn't really explain it, but it is a rule I can remember. I would appreciate hearing how anybody else remembers when to use shift() and when to use unshift().

Someone · Accepted Answer

Learn shell programming (https://tldp.org/LDP/Bash-Beginners-Guide/html/sect_09_07.ht...) or MS-DOS (https://learn.microsoft.com/en-us/windows-server/administrat...), and it won’t be a problem remembering what shift does.
Neither of those has unshift, but you can infer its meaning from knowing about shift.
I also think push and pop aren’t good names. append, respectively removelast are way better.

layer8 · Answer

Are you familiar with bit shifts? When you shift a 32-bit integer by one, for example, one bit will get shifted “off” the integer. In other words, the integer will have lost that bit.
Shift on an array similarly shifts an element off the array. Unshift puts an element back on the array.
Maybe more graphically: I you shift books on a shelf, the outermost book may fall off the shelf. To put it back on, you first need to “unshift” the books.
How I actually remember it is from Perl, where shift is commonly used to process the next argument from the argument array. And you rarely unshift.

mayoff · Answer

Unshift, like push, adds an element to the array.&ldquo;Unshift&rdquo;, like &ldquo;push&rdquo;, contains the letter &ldquo;u&rdquo;.

gregjor · Answer

Certainly you will remember the difference now, after writing this.
I remember the same way I remember anything else — by memorizing.
In British English “shift” means “move,” so shifting something off an array means moving it (into a variable). Un- as a prefix indicates negation or reversing in English. So you just need to remember what shift does, and unshift does the opposite, as indicated by the word.

rrishi · Answer

> Word "shift" is shorter than the word "unshift". Therefore shift() makes the array shorter.
> Word "unshift" is longer than the word "shift". Therefore unshift() makes the array longer.
This is quite useful as I too couldn't remember which is which. Thanks for sharing!

gqcwwjtg · Answer

Unshift is a weird word for the weird method of the four. You&rsquo;ve got a list. To use it as a stack you push and pop. To use it as a queue you push and shift. Unshift is the weird one.

sargstuff · Answer

Mix html with bit twiddle logic!html < is open block, html > is close block.< and and >> are logical shift right for array of bits.Looking at only 'logical value of 1'. Have to open/shift left before unopen/shift right to make thing correct. aka init variable to 0; shift left/push gives 1; shift right/removes aka pops the 1.html < pushes/shifts all the commands onto stack.html > pops all the commands todo off of the stack until reach < aka end of stack marker.

dataflow · Answer

The easiest way is learning what shift does in Bash, like another comment said, but if you're not going to do that:
- C also has functions called getc() and ungetc(), and they're analogous.
- "Doing" and "undoing" are actually the same in some sense: doing causes information loss, undoing causes information gain.

joshxyz · Answer

as a 6y js/ts dev i never really bothered, i just end up coming back to mdn docs whenever im about to use those.especially the internals of array sort method.

kondrei · Answer

I have this problem with splice and slice too

parentheses · Answer

bash is how i remember. shift consumes an argument starting at $1.this is how it works in all languagessame concept as

Mnemonic for shift() and unshift()?

Unshift, like push, adds an element to the array.
“Unshift”, like “push”, contains the letter “u”.

> Word "shift" is shorter than the word "unshift". Therefore shift() makes the array shorter.
> Word "unshift" is longer than the word "shift". Therefore unshift() makes the array longer.
This is quite useful as I too couldn't remember which is which. Thanks for sharing!

Unshift is a weird word for the weird method of the four. You’ve got a list. To use it as a stack you push and pop. To use it as a queue you push and shift. Unshift is the weird one.

as a 6y js/ts dev i never really bothered, i just end up coming back to mdn docs whenever im about to use those.
especially the internals of array sort method.

I have this problem with splice and slice too

bash is how i remember. shift consumes an argument starting at $1.
this is how it works in all languages
same concept as << (bit wise left shift)

Mnemonic for shift() and unshift()?

Unshift, like push, adds an element to the array.“Unshift”, like “push”, contains the letter “u”.

> Word "shift" is shorter than the word "unshift". Therefore shift() makes the array shorter.> Word "unshift" is longer than the word "shift". Therefore unshift() makes the array longer.This is quite useful as I too couldn't remember which is which. Thanks for sharing!

Unshift is a weird word for the weird method of the four. You’ve got a list. To use it as a stack you push and pop. To use it as a queue you push and shift. Unshift is the weird one.

as a 6y js/ts dev i never really bothered, i just end up coming back to mdn docs whenever im about to use those.especially the internals of array sort method.

I have this problem with splice and slice too

bash is how i remember. shift consumes an argument starting at $1.this is how it works in all languagessame concept as << (bit wise left shift)

Unshift, like push, adds an element to the array.
“Unshift”, like “push”, contains the letter “u”.

> Word "shift" is shorter than the word "unshift". Therefore shift() makes the array shorter.
> Word "unshift" is longer than the word "shift". Therefore unshift() makes the array longer.
This is quite useful as I too couldn't remember which is which. Thanks for sharing!

as a 6y js/ts dev i never really bothered, i just end up coming back to mdn docs whenever im about to use those.
especially the internals of array sort method.

bash is how i remember. shift consumes an argument starting at $1.
this is how it works in all languages
same concept as << (bit wise left shift)