const regex = /.*(\d{13}).*|.*/gm;
// Alternative syntax using RegExp constructor
// const regex = new RegExp('.*(\\d{13}).*|.*', 'gm')
const str = `Ceres Juice Apricot 12 x 1lt unit: 6001240102022
Ceres Juice Cranberry& Kiwi Juice 12 x 1lt... unit:
Ceres Juice Guava 12 x 1lt.. unit:6001240222829
Ceres Juice Orange 12x1lt... unit:
Ceres Juice Medley of Fruits 1L x 12 unit: 6001240100660`;
const subst = `$1`;
// The substituted value will be contained in the result variable
const result = str.replace(regex, subst);
console.log('Substitution result: ', result);
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for JavaScript, please visit: https://developer.mozilla.org/en/docs/Web/JavaScript/Guide/Regular_Expressions