const regex = /^[a-z](?=(?:[a-z]*\d){0,4}(?![a-z]*\d))(?=[a-z\d]{3,11}$)[a-z\d]+$/gm;
// Alternative syntax using RegExp constructor
// const regex = new RegExp('^[a-z](?=(?:[a-z]*\\d){0,4}(?![a-z]*\\d))(?=[a-z\\d]{3,11}$)[a-z\\d]+$', 'gm')
const str = `a1a2a3a4aaaa
a3333aaaaaaa
a1a2a3aaaaa2
a1a2a3
a222
aaaa
a2aa
f2fdfgdd
w333rrrrrrr4
rrrrrrrr4444
r22rrrrrrrrr
g4fff333ffff
333333333333
1111
1aaa
1aaaaaaaaaaa
1a2aaaaaaaaa
a1aaaaaaaaaaa
a11111aaaaaa
a122a3aaaaa2
a1a2a3a4a5aa
`;
// Reset `lastIndex` if this regex is defined globally
// regex.lastIndex = 0;
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