const regex = /\\\\.*?(?=[ &<]|\\[rn])/g;
// Alternative syntax using RegExp constructor
// const regex = new RegExp('\\\\\\\\.*?(?=[ &<]|\\\\[rn])', 'g')
const str = `this that
A space test: \\\\192.168.1.222\\more that
A & test: \\\\192.168.1.222\\jim\\john\\jack< that
A < test: \\\\192.168.1.222\\more<br> that
A \\n test: \\\\192.168.1.222\\nancy\\n that
A \\n test: \\\\192.168.1.222\\nancy\\n
A \\r test: \\\\192.168.1.222\\robert\\r that
A \\r test: \\\\192.168.1.222\\robert\\r
A & test: \\\\192.168.1.222\\more
the end
`;
const subst = `((($&)))`;
// 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