We Keep Coding

Print all even values in all object key end with odd value

I want to print all even values in all object key end with odd value but the coding I made just now is only specified for arr1, arr3, and arr5. Can anyone suggest me how to fix 'let oddArr' method (maybe in loop) so that when I changed arr1 into arr7, the result would be the same.
var num = {
arr1 : [1, 2, 3, 4, 5, 6, 7, 8, 9, 10],
arr2 : [11, 12, 13, 14, 15, 16, 17, 18, 19, 20],
arr3 : [21, 22, 23, 24, 25, 26, 27, 28, 29, 30],
arr4 : [31, 32, 33, 34, 35, 36, 37, 38, 39, 40],
arr5 : [41, 42, 43, 44, 45, 46, 47, 48, 49, 50],
};
let oddArr = [...num.arr1, ...num.arr3, ...num.arr5] //need some correction here
let evenNum = oddArr.filter(number => number % 2 == 0);
console.log(evenNum.toString());
//help me fix 'let oddArr' (maybe in loop method) so that when I changed the object of the array (e.g: arr1 -> arr7) it would come out with the same result
//the result/output should be 2,4,6,8,10,22,24,26,28,30,42,44,46,48,50 based on var num

You can try like below using for in loop and it works with any last character as odd.
var num = {
arr1: [1, 2, 3, 4, 5, 6, 7, 8, 9, 10],
arr2: [11, 12, 13, 14, 15, 16, 17, 18, 19, 20],
arr3: [21, 22, 23, 24, 25, 26, 27, 28, 29, 30],
arr4: [31, 32, 33, 34, 35, 36, 37, 38, 39, 40],
arr7: [41, 42, 43, 44, 45, 46, 47, 48, 49, 50]
};
let oddArr = [];
for (let key in num) {
if (key.charAt(key.length - 1) % 2 !== 0) {
oddArr = [...oddArr, ...num[key]];
}
}
let evenNum = oddArr.filter((number) => number % 2 === 0);
console.log(evenNum.toString());

You might want to use
let oddArr = Object.entries(num).filter( // filter key names
e => +e[0].replace("arr", '') % 2 !== 0 // replace "arr" and check if X in arrX is odd
).map(e => e[1]).flat() // merge values and flattern array
You can also make use of regex if the "arrX"-naming is not consistent:
+e[0].match(/\d+/) % 2 !== 0
See a working snippet below:
var num = {
arr1: [1, 2, 3, 4, 5, 6, 7, 8, 9, 10],
arr2: [11, 12, 13, 14, 15, 16, 17, 18, 19, 20],
arr3: [21, 22, 23, 24, 25, 26, 27, 28, 29, 30],
arr4: [31, 32, 33, 34, 35, 36, 37, 38, 39, 40],
arr5: [41, 42, 43, 44, 45, 46, 47, 48, 49, 50],
};
let oddArr = Object.entries(num).filter(
e => +e[0].replace("arr", '') % 2 !== 0
).map(e => e[1]).flat()
let evenNum = oddArr.filter(number => number % 2 == 0);
console.log(evenNum.toString());

This also works.
var num = {
arr1: [1, 2, 3, 4, 5, 6, 7, 8, 9, 10],
arr2: [11, 12, 13, 14, 15, 16, 17, 18, 19, 20],
arr3: [21, 22, 23, 24, 25, 26, 27, 28, 29, 30],
arr4: [31, 32, 33, 34, 35, 36, 37, 38, 39, 40],
arr5: [41, 42, 43, 44, 45, 46, 47, 48, 49, 50],
arr6: [51, 52, 53, 55, 55, 56, 57, 58, 59, 60],
arr7: [61, 62, 63, 66, 65, 66, 67, 68, 69, 70],
};
var evenNums = Object.keys(num).filter((item) => {
itemNum = item.replace("arr", "");
return itemNum % 2 !== 0;
}).map((o) => num[o]).flat().filter((x) => x % 2 == 0);
console.log(evenNums);

Changing an array in place using splice()

I'm trying to write a function that, given an array and n, returns the array with elements repeating no more than n times. I cannot change the order of the array.
Below is the code I have so far. What is perplexing me is that it works for most elements in a given array, but not for some others. I'm trying to find a rhyme or reason for the elements for which the code does not work.
function deleteNth(arr,n){
arr.forEach(function (item, index) {
var count = 0;
for (var i = 0; i < arr.length; i++) {
if (arr[i] === item) {
count++;
while (count > n) {
var remove = arr.lastIndexOf(item);
arr.splice(remove, 1);
count--;
}
}
}
});
return arr;
}
var x = deleteNth([7, 26, 21, 41, 43, 2, 26, 24, 10, 26, 10, 10, 24, 35, 35,
35, 43, 26, 41, 7, 24, 24, 21, 24, 10, 35, 10, 7, 24, 7, 35, 26, 41,
35, 2, 43, 24, 2, 41, 26, 41, 7, 7, 26, 2, 10, 43, 10, 35, 41, 24, 7,
2, 2, 7, 2, 26, 24, 26, 43, 43, 21, 10, 28, 10], 2);
console.log(x);
Currently returns this...
[7, 26, 21, 41, 43, 2, 26, 24, 10, 10, 10, 24, 35, 35, 43, 41, 7, 21,
41, 2, 43, 28]
But I should get this...
[7, 26, 21, 41, 43, 2, 26, 24, 10, 10, 24, 35, 35, 43, 41, 7, 21, 2,
28]
Any insight into where I'm going wrong would be sincerely appreciated.

The logic of where you places the while loop is wrong, you need to place it outside of the for loop.
function deleteNth(arr, n) {
arr.forEach(function(item, index) {
var count = 0;
for (var i = 0; i < arr.length; i++) {
if (arr[i] === item) {
count++;
}
}
while (count > n) {
var remove = arr.lastIndexOf(item);
arr.splice(remove, 1);
count--;
}
});
return arr;
}
var x = deleteNth([7, 26, 21, 41, 43, 2, 26, 24, 10, 26, 10, 10, 24, 35, 35,
35, 43, 26, 41, 7, 24, 24, 21, 24, 10, 35, 10, 7, 24, 7, 35, 26, 41,
35, 2, 43, 24, 2, 41, 26, 41, 7, 7, 26, 2, 10, 43, 10, 35, 41, 24, 7,
2, 2, 7, 2, 26, 24, 26, 43, 43, 21, 10, 28, 10
], 2);
console.log(x);
Why? Because when you are doing your loop and you remove things from it, you shift things back down. So when you have two items side by side and you remove the first the second one shifts down one spot to fill what you just removed. The i does not change so you do not check the item that just filled the gap.
What would I do? I would just keep track of the items as I get to it and if I have not gone over the max append it.
function cleanUp (arr, max) {
const cnts = {} // keep track of what we find
return arr.reduce((a, i) => { // loop over the array index by index
cnts[i] = (cnts[i] || 0) + 1; // mark that I seen the number
if (cnts[i] <= max) { // check to see if we are under the max
a.push(i) //if we are, add it to an arry
}
return a // return the array for reduce
}, [])
}
console.log(cleanUp([7, 26, 21, 41, 43, 2, 26, 24, 10, 26, 10, 10, 24, 35, 35,
35, 43, 26, 41, 7, 24, 24, 21, 24, 10, 35, 10, 7, 24, 7, 35, 26, 41,
35, 2, 43, 24, 2, 41, 26, 41, 7, 7, 26, 2, 10, 43, 10, 35, 41, 24, 7,
2, 2, 7, 2, 26, 24, 26, 43, 43, 21, 10, 28, 10], 2))

This code works:
function deleteNth(arr,n){
var rem = new Array(), new_arr = new Array();
arr.forEach(function (item, index) {
if(!rem[item]) rem[item]=0;
if(rem[item]<n){
new_arr.push(item);
rem[item]++;
}
});
return new_arr;
}
console.log(deleteNth([7, 26, 21, 41, 43, 2, 26, 24, 10, 26, 10, 10, 24, 35, 35, 35, 43, 26, 41, 7, 24, 24, 21, 24, 10, 35, 10, 7, 24, 7, 35, 26, 41, 35, 2, 43, 24, 2, 41, 26, 41, 7, 7, 26, 2, 10, 43, 10, 35, 41, 24, 7, 2, 2, 7, 2, 26, 24, 26, 43, 43, 21, 10, 28, 10], 2));

All of your code is true. Just bring that while out of for loop.
function deleteNth(arr, n) {
arr.forEach(function(item, index) {
var count = 0;
for (var i = 0; i < arr.length; i++) {
if (arr[i] === item) {
count++;
}
}
while (count > n) {
var remove = arr.lastIndexOf(item);
arr.splice(remove, 1);
count--;
}
});
return arr;
}
var x = deleteNth([7, 26, 21, 41, 43, 2, 26, 24, 10, 26, 10, 10, 24, 35, 35,
35, 43, 26, 41, 7, 24, 24, 21, 24, 10, 35, 10, 7, 24, 7, 35, 26, 41,
35, 2, 43, 24, 2, 41, 26, 41, 7, 7, 26, 2, 10, 43, 10, 35, 41, 24, 7,
2, 2, 7, 2, 26, 24, 26, 43, 43, 21, 10, 28, 10
], 2);
console.log(x);

I like Nina's filter (probably performs better as well) but you can also use reduce:
function deleteNth(arr,n){
return arr.reduce(
([result,map],item)=>{
const count = (map.get(item)||0)+1;
return [
//do not add if more than n of this item have been added already
(count<=n)?result.concat(item):result,
map.set(item,count)//set the new count for this item and return map
]
},
[[],new Map()]//initial value for result and map
)[0];
}
Here is an example using filter and a Map:
function deleteNth(arr,n){
const map = new Map();
return arr.filter(
item=>{
const count = (map.get(item)||0)+1;
map.set(item,count);
return (count<=n);
}
);
}
console.log(deleteNth([1,2,3,2,4,2,5], 2));

If you really want to do it in place, then this answer is not for you. (I think there are very good reasons to work with immutable data, but if you want to mutate, one of the other answers should do it.
Here's one solution that simply keeps a count of each item seen as you go, and filters out those we've seen too often:
const deleteNth = (arr, n) => {
const found = new Map()
return arr.filter(val => {
found.set(val, (found.get(val) || 0) + 1)
return found.get(val) <= n
})
}
const result = deleteNth([7, 26, 21, 41, 43, 2, 26, 24, 10, 26, 10, 10, 24, 35, 35, 35, 43, 26, 41, 7, 24, 24, 21, 24, 10, 35, 10, 7, 24, 7, 35, 26, 41, 35, 2, 43, 24, 2, 41, 26, 41, 7, 7, 26, 2, 10, 43, 10, 35, 41, 24, 7, 2, 2, 7, 2, 26, 24, 26, 43, 43, 21, 10, 28, 10], 2)
console.log(result)
One other note: It might offer a nicer API if you choose:
deleteNth = (n) => (arr) => { /* ... */ }
This way you could pass just the repetition count and get back a new function which filters an array.
(Also, this does not sound like a good name for something that delete's all repetitions of a value after the nth one.)

For a fast mutating version, you could use a single while loop, a hash table for counting the items and an adjustment of the index if a splice happens.
function deleteNth(array, n) {
var counter = Object.create(null),
i = 0, v;
while (i < array.length) {
v = array[i];
if (!counter[v]) {
counter[v] = 0;
}
if (++counter[v] > n) {
array.splice(i, 1);
continue;
}
i++;
}
return array;
}
console.log(deleteNth([7, 26, 21, 41, 43, 2, 26, 24, 10, 26, 10, 10, 24, 35, 35, 35, 43, 26, 41, 7, 24, 24, 21, 24, 10, 35, 10, 7, 24, 7, 35, 26, 41, 35, 2, 43, 24, 2, 41, 26, 41, 7, 7, 26, 2, 10, 43, 10, 35, 41, 24, 7, 2, 2, 7, 2, 26, 24, 26, 43, 43, 21, 10, 28, 10], 2));
.as-console-wrapper { max-height: 100% !important; top: 0; }
A better way is to use filter and return a new array.
function deleteNth(array, n) {
var counter = Object.create(null);
return array.filter(v => (counter[v] = (counter[v] || 0) + 1) <= n);
}
console.log(deleteNth([7, 26, 21, 41, 43, 2, 26, 24, 10, 26, 10, 10, 24, 35, 35, 35, 43, 26, 41, 7, 24, 24, 21, 24, 10, 35, 10, 7, 24, 7, 35, 26, 41, 35, 2, 43, 24, 2, 41, 26, 41, 7, 7, 26, 2, 10, 43, 10, 35, 41, 24, 7, 2, 2, 7, 2, 26, 24, 26, 43, 43, 21, 10, 28, 10], 2));
.as-console-wrapper { max-height: 100% !important; top: 0; }

I am stuck on a quiz in Udacity for JavaScript on Multi-dimensional arrays.

The quiz is about a multidimensional array and wants us to use a nested for loop to cycle through each element and replace the values that are divisible by 2 with the strings 'even' and 'odd' for even and odd numbers respectively. I cannot print out the array with the numbers divisible by 2 on to the console with the added string.
I have tried using .slice() and .splice() also but that did not get me the desired results either. Below is my latest attempt.
Programming Quiz - Multi-dimensional Arrays:
Question: Use a nested for loop to take the numbers array below and replace all of the values that are divisible by 2 (even numbers) with the string "even" and all other numbers with the string "odd".
var numbers = [
[243, 12, 23, 12, 45, 45, 78, 66, 223, 3],
[34, 2, 1, 553, 23, 4, 66, 23, 4, 55],
[67, 56, 45, 553, 44, 55, 5, 428, 452, 3],
[12, 31, 55, 445, 79, 44, 674, 224, 4, 21],
[4, 2, 3, 52, 13, 51, 44, 1, 67, 5],
[5, 65, 4, 5, 5, 6, 5, 43, 23, 4424],
[74, 532, 6, 7, 35, 17, 89, 43, 43, 66],
[53, 6, 89, 10, 23, 52, 111, 44, 109, 80],
[67, 6, 53, 537, 2, 168, 16, 2, 1, 8],
[76, 7, 9, 6, 3, 73, 77, 100, 56, 100]
];
My code:
//create a nested for loop to cycle through each row and column
for(let row = 0; row < numbers.length; row++){
for(let col = 0; col < numbers.length; col++){
//if the even numbers in each row and column are divisible by 2, replace those
//numbers with the word even
if(numbers % 2 === 0){
numbers[row] += 'even';
}
}
}
console.log(numbers);

You're real close! It comes down to how you're referencing the index in the 2-dimensional array. Iterating over it in a nested for loop requires first that we iterate through the rows, then the columns. In your example, you were actually iterating over the columns twice. In order to fix this, you would simply iterate over the row index of the numbers array in the nested for loop:
for(let row = 0; row < numbers.length; row++){
for(let col = 0; col < numbers[row].length; col++){
Then finally you will need to set the target index numbers[row][col] to even. In your example you used the addition assignment operator +=, which performs what is string concatenation. Instead of simply changing the index value to 'even', the += would actually add the word 'even' to the end of the number. So the index output would actually read something like 156even. Just drop the plus sign in order to reassign the index to even:
numbers[row][col] = 'even';
var numbers = [
[243, 12, 23, 12, 45, 45, 78, 66, 223, 3],
[34, 2, 1, 553, 23, 4, 66, 23, 4, 55],
[67, 56, 45, 553, 44, 55, 5, 428, 452, 3],
[12, 31, 55, 445, 79, 44, 674, 224, 4, 21],
[4, 2, 3, 52, 13, 51, 44, 1, 67, 5],
[5, 65, 4, 5, 5, 6, 5, 43, 23, 4424],
[74, 532, 6, 7, 35, 17, 89, 43, 43, 66],
[53, 6, 89, 10, 23, 52, 111, 44, 109, 80],
[67, 6, 53, 537, 2, 168, 16, 2, 1, 8],
[76, 7, 9, 6, 3, 73, 77, 100, 56, 100]
];
for(let row = 0; row < numbers.length; row++){
for(let col = 0; col < numbers[row].length; col++){ //iterate over the n-th index of numbers[]
if(numbers[row][col] % 2 === 0){ //numbers[row][col] points to the nested index
numbers[row][col] = 'even'; //set index to 'even'
}
}
}
console.log(numbers);
This video is a nice explanation of how iterating over 2d arrays works: https://www.youtube.com/watch?v=qdT1P2qmsmU
The video is using Java, but the idea is exactly the same.
Hope this helps! Multi-dimensional arrays are tough to wrap your brain around!

Transform a 9x9 Matrix so that each row is a 3x3 Block

I have the following example data:
[0] = {01,02,03, 04,05,06, 07,08,09}
[1] = {11,12,13, 14,15,16, 17,18,19}
[2] = {21,22,23, 24,25,26, 27,28,29}
[3] = {31,32,33, 34,35,36, 37,38,39}
[4] = {41,42,43, 44,45,46, 47,48,49}
[5] = {51,52,53, 54,55,56, 57,58,59}
[6] = {61,62,63, 64,65,66, 67,68,69}
[7] = {71,72,73, 74,75,76, 77,78,79}
[8] = {81,82,83, 84,85,86, 87,88,89}
To create the new matrix I did this, Knowing it static 9x9
var grid2=[[],[]];
grid2.push([grid[0][0],grid[0][1], grid[0][2],grid[1][0],grid[1][1], grid[1][2],grid[2][0],grid[2][1], grid[2][2]]);
grid2.push([grid[3][0],grid[3][1], grid[3][2],grid[4][0],grid[4][1], grid[4][2],grid[5][0],grid[5][1], grid[5][2]]);
grid2.push([grid[6][0],grid[6][1], grid[6][2],grid[7][0],grid[7][1], grid[7][2],grid[8][0],grid[8][1], grid[8][2]]);
grid2.push([grid[0][3],grid[0][4], grid[0][5],grid[1][3],grid[1][4], grid[1][5],grid[2][3],grid[2][4], grid[2][5]]);
grid2.push([grid[3][3],grid[3][4], grid[3][5],grid[4][3],grid[4][4], grid[4][5],grid[5][3],grid[5][4], grid[5][5]]);
grid2.push([grid[6][3],grid[6][4], grid[6][5],grid[7][3],grid[7][4], grid[7][5],grid[8][3],grid[8][4], grid[8][5]]);
grid2.push([grid[0][6],grid[0][7], grid[0][8],grid[1][6],grid[1][7], grid[1][8],grid[2][6],grid[2][7], grid[2][8]]);
grid2.push([grid[3][6],grid[3][7], grid[3][8],grid[4][6],grid[4][7], grid[4][8],grid[5][6],grid[5][7], grid[5][8]]);
grid2.push([grid[6][6],grid[6][7], grid[6][8],grid[7][6],grid[7][7], grid[7][8],grid[2][6],grid[8][7], grid[8][8]]);
This works, but my question is, can this be done more efficiently / elegantly.
The point of this, is part of a larger code base, that takes the matrix and validates if it is a Sudoku solution.

You can use a simple algorithm for this
let idx = [0, 1, 2], idy = [0, 1, 2];
let result = [];
for(let i=0; i<9; i+=3){
for(let j=0; j<9; j+=3){
idx.forEach(e => {
idy.forEach(f => {
result.push(arr[i+e][j+f]);
})
})
}
}

You could take a nested approach for transforming the given 2D to a 4D array.
var data = [[1, 2, 3, 4, 5, 6, 7, 8, 9], [11, 12, 13, 14, 15, 16, 17, 18, 19], [21, 22, 23, 24, 25, 26, 27, 28, 29], [31, 32, 33, 34, 35, 36, 37, 38, 39], [41, 42, 43, 44, 45, 46, 47, 48, 49], [51, 52, 53, 54, 55, 56, 57, 58, 59], [61, 62, 63, 64, 65, 66, 67, 68, 69], [71, 72, 73, 74, 75, 76, 77, 78, 79], [81, 82, 83, 84, 85, 86, 87, 88, 89],],
result = data.reduce((r, a, i) => (
a.forEach((b, j) =>
[Math.floor(i / 3), Math.floor(j / 3), i % 3].reduce(
(s, k) => s[k] = s[k] || [],
r
)[j % 3] = b),
r),
[]);
console.log(result);
.as-console-wrapper { max-height: 100% !important; top: 0; }

Convert buffer to array

I am setting memcached with
$memcached->set("item" , ["1" => "hello"]);
anything work in PHP ,
In Node.js with memcached plugin , I get a buffer instead of array in result
<Buffer 61 3a 25 61 34 3a>
I can not convert such buffer to array
In Node.js :
memcached.get("item" , function(err, data) {
console.log(data);
}
Do you have any way ?

arr = [...buffer]
ES6 introduced a lot of other features, besides buffers.
You can even easily append like this:
arr.push(...buffer)
The ... operator expands enumerables such as arrays and buffers when used in array. It also expands them into separate function arguments.
Yes, it's also faster:
... : x100000: 835.850ms
Slice call from prototype : x100000: 2118.513ms
var array,
buffer = new Buffer([1, 4, 4, 5, 6, 7, 5, 3, 5, 67, 7, 4, 3, 5, 76, 234, 24, 235, 24, 4, 234, 234, 234, 325, 32, 6246, 8, 89, 689, 7687, 56, 54, 643, 32, 213, 2134, 235, 346, 45756, 857, 987, 0790, 89, 57, 5, 32, 423, 54, 6, 765, 65, 745, 4, 34, 543, 43, 3, 3, 3, 34, 3, 63, 63, 35, 7, 537, 35, 75, 754, 7, 23, 234, 43, 6, 247, 35, 54, 745, 767, 5, 3, 2, 2, 6, 7, 32, 3, 56, 346, 4, 32, 32, 3, 4, 45, 5, 34, 45, 43, 43]),
iter = 100000;
array = buffer;
console.time("... : x" + iter);
for (var i = iter; i--;) array = [...buffer]
console.timeEnd("... : x" + iter);
console.time("Apply/call/etc : x" + iter);
for (var i = iter; i--;) array = Array.prototype.slice.call(buffer, 0)
console.timeEnd("Apply/call/etc : x" + iter);

There is another way to convert to array of integers
Using toJSON()
Buffer.from('Text of example').toJSON()
{ type: 'Buffer',data: [ 84, 101, 120, 116, 32, 111, 102, 32, 101, 120, 97, 109, 112, 108, 101 ] }
// simple get data
Buffer.from('Text of example').toJSON().data
[ 84, 101, 120, 116, 32, 111, 102, 32, 101, 120, 97, 109, 112, 108, 101 ]
Example of benchmark
// I took this from #user4584267's answer
const buffer = new Buffer([1, 4, 4, 5, 6, 7, 5, 3, 5, 67, 7, 4, 3, 5, 76, 234, 24, 235, 24, 4, 234, 234, 234, 325, 32, 6246, 8, 89, 689, 7687, 56, 54, 643, 32, 213, 2134, 235, 346, 45756, 857, 987, 0790, 89, 57, 5, 32, 423, 54, 6, 765, 65, 745, 4, 34, 543, 43, 3, 3, 3, 34, 3, 63, 63, 35, 7, 537, 35, 75, 754, 7, 23, 234, 43, 6, 247, 35, 54, 745, 767, 5, 3, 2, 2, 6, 7, 32, 3, 56, 346, 4, 32, 32, 3, 4, 45, 5, 34, 45, 43, 43]);
let array = null;
const iterations = 100000;
console.time("...buffer");
for (let i = iterations; i=i-1;) array = [...buffer]
console.timeEnd("...buffer");
console.time("array.prototype.slice.call");
for (let i = iterations; i=i-1;) array = Array.prototype.slice.call(buffer, 0)
console.timeEnd("array.prototype.slice.call");
console.time("toJSON().data");
for (let i = iterations; i=i-1;) array = buffer.toJSON().data
console.timeEnd("toJSON().data");
OUTPUT
...buffer: 559.932ms
array.prototype.slice.call: 1176.535ms
toJSON().data: 30.571ms
or if you want more profesional and custom function in Buffer use this:
Buffer.prototype.toArrayInteger = function(){
if (this.length > 0) {
const data = new Array(this.length);
for (let i = 0; i < this.length; i=i+1)
data[i] = this[i];
return data;
}
return [];
}
Example of benchmark:
const buffer = new Buffer([1, 4, 4, 5, 6, 7, 5, 3, 5, 67, 7, 4, 3, 5, 76, 234, 24, 235, 24, 4, 234, 234, 234, 325, 32, 6246, 8, 89, 689, 7687, 56, 54, 643, 32, 213, 2134, 235, 346, 45756, 857, 987, 0790, 89, 57, 5, 32, 423, 54, 6, 765, 65, 745, 4, 34, 543, 43, 3, 3, 3, 34, 3, 63, 63, 35, 7, 537, 35, 75, 754, 7, 23, 234, 43, 6, 247, 35, 54, 745, 767, 5, 3, 2, 2, 6, 7, 32, 3, 56, 346, 4, 32, 32, 3, 4, 45, 5, 34, 45, 43, 43]);
let array = null;
const iterations = 100000;
console.time("toArrayInteger");
for (let i = iterations; i=i-1;) buffer.toArrayInteger();
console.timeEnd("toArrayInteger");
Ouput:
toArrayInteger: 28.714ms
Note: In the last example I copied a function from Buffer.toJSON and custom it a lite

Here you go:
var buffer = new Buffer([1,2,3])
var arr = Array.prototype.slice.call(buffer, 0)
console.log(arr)

I haven't used memcached so I am not sure just what this buffer represents or what you want to have instead. Sorry. Here is a function to split a buffer up into an array of bytes. More at node.js Buffer docs, hope it helps!
var hex = new Buffer("613a2561343a", "hex");
var l = hex.length; // in bytes
var output = [];
for(var i = 0; i < l; i++){
var char = hex.toString('hex',i,i+1); // i is byte index of hex
output.push(char);
};
console.log(output);
// output: [ '61', '3a', '25', '61', '34', '3a' ]

You can also use Array.from:
memcached.get("item" , function(err, data) {
console.log(Array.from(data));
}

I have a solution, although I am currently trying to find a better one:
function bufToArray(buffer) {
let array = new Array();
for (data of buffer.values()) array.push(data);
return array;
}
EDIT : I found a simpler way:
var buffer = Buffer.from('NodeJS rocks!')
var array = new Function(`return [${Array.prototype.slice.call(buffer, 0)}]`)
But, like someone already said, [...buffer] is faster (and more code efficient).
You can also use new Uint8Array(buffer [, byteOffset [, length]]);

In interent , there was no information about that , but I have found the convert way
In nodejs , I have to use :
var arrayobject = phpjs.unserialize(data.toString());
but , it is very stupid way for getting array , it seem that php serilzie the data when setting memcache .