Амир

display: flex;
flex-flow: column nowrap;

messages.sort((a, b) => {
  [ a, b ] = [ a, b ].map(n => sortableLanguages.indexOf(n.language));
  return a === -1 ? 1 : b === -1 ? -1 : a - b;
});

const sorted = (arr, key) => arr
  .map(n => [ n, key(n) ])
  .sort((a, b) => a[1] - b[1])
  .map(n => n[0]);


const order = Object.fromEntries(sortableLanguages.map((n, i) => [ n, i + 1 ]));
const sortedMessages = sorted(messages, n => order[n.language] || Number.MAX_SAFE_INTEGER);

// или

function sorted(arr, order, key) {
  const ordered = new Map(order.map(n => [ n, [] ]));
  const unordered = [];

  arr.forEach(n => (ordered.get(key(n)) || unordered).push(n));

  return [].concat(...ordered.values(), unordered);
}


const sortedMessages = sorted(messages, sortableLanguages, n => n.language);

const str = "Error.0.Value : This is error for item 0.\r\nError.1.Value : This is error for item 1 and this item is exist.";

let result = {};

str.split("\r\n").forEach(item => Object.assign(result, { [`someinput[${item.split(" : ")[0].match(/\d+/)}]`]: item.split(" : ")[1] }));

/*
{
  "someinput[0]": "This is error for item 0.",
  "someinput[1]": "This is error for item 1 and this item is exist."
}
*/

echo apply_filters( 'the_content', $post_parts['extended'] );

function myFunc(data) { console.log(data) }
console.log( myFunc('test') ) => выведеть в консоль 'test'
console.log( myFunc ) => выведеть в консоль function myFunc ...