Функція повертає скорочений до заданої кількості символів рядок із трьома крапками у кінці.

endStringWithThreeDots.js

// https://gist.github.com/i-havr/deae1ca8874c01d0ccc1e396714af687

// v0
const LIMIT = 30;

const endStringWithThreeDots = (str) => {
  if (str.length <= LIMIT) {
    return str;
  } else {
    const updatedString = str.slice(0, LIMIT - 3) + "...";
    return updatedString;
  }
};


// shorter version:
const endStringWithThreeDots = (str, limit = 30) =>
  (str.length <= limit) ? str : str.slice(0, limit - 3) + "...";

// unicode compatible:
const endStringWithThreeDots = (str, limit = 30) =>
  (str.length <= limit) ? str : Array.from(str).slice(0, limit - 3).join("") + "...";

// unicode compatible fixed:
function endStringWithThreeDots (str, limit = 30) {
  var A = Array.from(str);
  return (A.length <= limit) ? str : A.slice(0, limit - 3).join("") + "...";
}

console.log(endStringWithThreeDots("dgdfsdf"));
console.log(endStringWithThreeDots("dgdfsdf",5));
console.log(endStringWithThreeDots("dgdfsddsfdsffdsafjkdsakdshakhdaskhfkadsjhfkdsfjkdsggdsjfddsf"));
console.log(endStringWithThreeDots("dgdfsddsfdsffdsafjkdsakdshakhdaskhfkadsjhfkdsfjkdsggdsjfddsf",15));
/*
dgdfsdf
dg...
dgdfsddsfdsffdsafjkdsakdsha...
dgdfsddsfdsf...
*/