How to compress an array to reduce its number of elements in Javascript?

July 30, 2022

I have an array containing numbers, in that array there’re some numbers that occur many times in consecutive order one after the other, and I want to compress those repeated numbers into a very specific format ‘Number*Times’ to reduce the size of the array:

input:  [0, 1, 2, 0, 0, 0, 3, 2, 0, 0, 0, 0, 0, 0, 5, 6, 0]
         ---------^^^^^^^^^-----^^^^^^^^^^^^^^^^^^^--------
output: [0, 1, 2,'0x3', 3, 2, '0x6', 5, 6, 0]

let array = [0, 1, 2, 0, 0, 0, 3, 2, 0, 0, 0, 0, 0, 0, 5, 6, 0];
let string = array.toString();
let string_compressed = string.replace(/(\d+,)(\1)+/g, (x) => {
  return "Number*" + x.split(",").length + ",";
});
let array_compressed = string_compressed
  .split(",")
  .map((x) => (isNaN(Number(x)) ? x : Number(x)));
console.log(array_compressed); //[0, 1, 2, 'Number*4', 3, 2, 'Number*7', 5, 6, 0]

I don’t know how to get the number that repeated so I put Number instead!
I used regex to solve it, I know if you think to solve problem with regex, they become two problems!
BUT Guys I’m sure this isn’t the efficient way to solve this problem, And there’re other ways to solve it!
what do you suggest if you want to solve this problem?

>Solution :

Because your regex to find how many numbers repeat already only matches numbers that are in consecutive order in your array, you can simply just take the first index of the x.split(",") array and return that. I attached the code snippet below:

let array = [0, 1, 2, 0, 0, 0, 3, 2, 0, 0, 0, 0, 0, 0, 5, 6, 0];
let string = array.toString();
let string_compressed = string.replace(/(\d+,)(\1)+/g, (x) => {
  return x.split(",")[0] + "*" + x.split(",").length + ",";
});
let array_compressed = string_compressed
  .split(",")
  .map((x) => (isNaN(Number(x)) ? x : Number(x)));
console.log(array_compressed);