const regex = /^(\w+)\s+(\w+)\s*,\s*(\w+).*/gmu;
// Alternative syntax using RegExp constructor
// const regex = new RegExp('^(\\w+)\\s+(\\w+)\\s*,\\s*(\\w+).*', 'gmu')
const str = `RUIZ JIMENO, ALBERTO ADRIAN => RUIZJIMENOALBERTO
LÓPEZ FAUSTO, CATALINA DE MIGUEL => LOPEZFAUSTOCATALINA`;
const subst = `\1\2\3`;
// 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