const regex = /^(\S+) (?=(?s:.)*(\1.*)).*/gm;
// Alternative syntax using RegExp constructor
// const regex = new RegExp('^(\\S+) (?=(?s:.)*(\\1.*)).*', 'gm')
const str = `user1 jul/12/12
user5 jul/13/13
user1 jul/14/12
user1 jul/12/12
user5 jul/13/13
user1 jul/14/12
user3 jan/12/12
user1 jul/12/12
user5 jul/13/13
user1 jul/14/12
user1 jul/12/12
user5 jul/13/13
user1 jul/14/12
user1 jul/12/12
user6 aug/06/06
user5 jul/13/13
user1 jul/14/12
user1 jul/12/12
user5 jul/13/13
user1 jul/14/12
user1 aug/12/12
user5 feb/13/13
user1 dec/14/12
user1 jul/12/12
user5 jul/13/13
user1 jul/14/12
user2 jun/15/14`;
let m;
while ((m = regex.exec(str)) !== null) {
// This is necessary to avoid infinite loops with zero-width matches
if (m.index === regex.lastIndex) {
regex.lastIndex++;
}
// The result can be accessed through the `m`-variable.
m.forEach((match, groupIndex) => {
console.log(`Found match, group ${groupIndex}: ${match}`);
});
}
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