Fastest way to move first element to the end of an Array

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I'm wondering what is the fastest way in JavaScript to move an element from the beginning of an Array to the end. For example if we have

[8,1,2,3,4,5,6,7]

And we want: [1,2,3,4,5,6,7,8]

I want to move the first element to the end. I was thinking about switching element 0 with element 1, after that switching element 1 with element 2 and so on until the 8 is at the and (basically how bubblesort works). I was wondering if there is a faster way to bring the first element to the end.

I will be using small Arrays (around 10 elements), and I want to avoid shift() since it's pretty slow.

This is what I have now on chrome it's 45% faster than normal shift+push: http://jsperf.com/shift-myfunc

The arrays will have objects in them for a game.

var ary = [8,1,2,3,4,5,6,7];
ary.push(ary.shift());  // results in [1, 2, 3, 4, 5, 6, 7, 8] 

jsFiddle example

var ary = [8,1,2,3,4,5,6,7];

console.log("Before: " + ary);

ary.push(ary.shift());  // results in [1, 2, 3, 4, 5, 6, 7, 8] 

console.log("After: " + ary);

javascript, var ary = [8,1,2,3,4,5,6,7]; ary.push(ary.shift()); // results in [1, 2, 3, 4, 5, 6, 7, 8]. jsFiddle example. var ary = [8,1,2,3,4,5,6,7]; console.log("Before:  If you need to do it several hundred thousand times, you might be using the wrong data structure. A queue would, in fact, be faster than an array, compiler instructions notwithstanding. A queue maintains start and end pointers, so it can remove the first element (or the last element) in O(1) time (vs.

How to move first element to the end of array, How do I remove the first element from an array? To move an element from one position to other (swap) you need to – Create a temp variable and assign the value of the original position to it. Now, assign the value in the new position to original position. Finally, assign the value in the temp to the new position.

Use splice to get the first element

var first = array.splice(0,1);

Then push to make if the last.

Since the return value of the splice method is an array, you have to say

array.push(first[0]);

Working example here: JSFIDDLE

Array.prototype.shift(), How do you add a number to the end of an array? Double the first element and move zero to end Move all zeroes to end of array Given an array of random numbers, Push all the zero’s of a given array to the end of the array. For example, if the given arrays is {1, 9, 8, 4, 0, 0, 2, 7, 0, 6, 0}, it should be changed to {1, 9, 8, 4, 2, 7, 6, 0, 0, 0, 0}.

Just in case you want to put any element to the end:

var ary = [8,1,2,3,4,5,6,7];
ary.push(ary.splice(position, 1)[0]);

for position just wrap this in a forEach.

JavaScript: Remove Element from an Array, using push , to the beginning using unshift , or to the middle using splice . Hi I'm trying to modify an array so that I remove the first element of an array completely (ie decrease the size of the array). Then once I've done that I would like to add a new element (increase the size of the array).

And here is a sweet ES6 version

let arr = [1,2,3,4,5,6]

const [first, ...rest] = arr;
arr = [...rest,first]

How to Add Elements to an Array in JavaScript, How do you insert an item at the beginning of an array in JavaScript? It's more a rotate than shift. You need to save the last value when you start (9 in this case), shuffle all the elements into the next slot up starting with the second to last. Then set the saved value into position zero. Your main's logic is correct, but syntactically incorrect. main should always return an int.

JavaScript, Four useful methods to add or remove to the end or beginning of arrays in Pop, Push, Shift and Unshift Array Methods in JavaScript Drag & Drop Elements. If you insert an item, it has to shift all the elements after that item to make room to insert it. These shifts can get very expensive if your array is very big. Since you know that you want to end up with the same number of elements in the list, doing a swap like this allows you to "move" an element to another location in the list very

Pop, Push, Shift and Unshift Array Methods in JavaScript, When you need to move the first element in an array to the last position, follow this tip. You can use the returned function array.shift() as input to the function  The speed might vary between the two depending on the type of data you're dealing with. If you know the size of the array you'll end up with ahead of time, then I believe the fastest way to do it is to initialize the array ahead of time and then replace array elements. You can use the index terminal of a loop to select the spot to replace.

Moving the first item to the last position in the array JavaScript, In computer science, this means an ordered collection of elements which supports two operations: push appends an element to the end. shift get an element from the beginning, advancing the Extracts the first element of the array and returns it: Methods push/pop run fast, while shift/unshift are slow. You can move the array elements one by one by using a temporary variable. Now the array content are shifted by 1 towards left.

Comments
  • It's a shame how OP is looking for the fastest way and not just a and people are giving general answers without explaining why they're faster/slower than alternatives. FGITW I guess. OP, what is your specific use case? What browsers are you targeting? How big is the array (are they always ~8 elements? Are they 10K elements?), if you want real benchmarking you need to be a lot more specific.
  • Thanks for editing to clarify - next round: are they arrays sparse like [1,2,,,5,8] or are they always full (like your example), do they always contain integers only? What browsers/engines are you targeting and how many iterations of these sort of shifts do you need to do per second at most?
  • @BenjaminGruenbaum It would have helped if the OP would have stated what they tried up front and maybe there would not have been general answers. Effort in question = effort in answer. Simple tests with JSPerf would on been nice. :)
  • @epascarello True - the fastest way to do something is very dependent here- on the target JS engine, on the array size, on what it contains and so on - I'm also still waiting to be convinced OP really needs it to be that fast and at what expense (if he is rotating a lot for example it might be good to keep a copy of the array concatenated to itself and slice it, work with a typed array or use other useful tricks). I know you and j08691 are definitely good guys around here from knowing a bunch of your other answer but answering one just seemed kind of pointless given the ambiguity.
  • For any future bypassers, how this works is using the Shift function. It removes the first item in an array and then returns it. So in other words, this code removes the first item in the array and then adds it again - making it go to the bottom of the array.
  • nice and elegant.
  • very well done... I was looking for the opposite but came up on this answer so after some quick research here is the opposite way of doing the above... ary.unshift(ary.pop());
  • I wanted to avoid the use of shift since it's pretty slow.
  • Than say that in your question!
  • @user2815780 - Perhaps you should post what you've already tried in your question, including stats to show what's fast and slow?
  • I updated my answer with ways to do it and a JSPerf. I am sure my loop answer can be improved, I just threw it together as a break from my real work.
  • note that splice() returns an array so the test called "splice-push" (my personal preference) is not 100% correct. Should be: var b = arr.splice(0, 1); arr.push(b[0]);
  • ary.push(ary.slice(position, 1)); is wrong and would result in [8,1,2,3,4,5,6,7,Array[1] if position was 0, or [8,1,2,3,4,5,6,7,Array[0] if position was 1. I assume you wanted splice rather than slice. Cause slice doesn't remove items, and it uses the arg list start, end rather than start, deleteCount. Either way, both slice/splice return an Array, so you have to push the first item of the arr, rather than the arr itself. I fixed the code: ary.push(ary.splice(0, 1)[0]);