const regex = /^(([1-9]\d{0,2}((,\d{3})*|(\d{3})*))|0?)(\.\d+)?$/gm;
// Alternative syntax using RegExp constructor
// const regex = new RegExp('^(([1-9]\\d{0,2}((,\\d{3})*|(\\d{3})*))|0?)(\\.\\d+)?$', 'gm')
const str = `Capture the following numbers
1
0
1223
332243243423243243243423423243
12
1000000000
111,000,000
1000.000398
1,123,333.2222222
1.22222222
1,234,345,673,345,345,345.123455
1222222222
0.123345
.1234
012,312
.12332
1000.122.122
1,231,423,434.3746472773640000000000
Don't Capture:
2000..0000
,111.45
start of line
#first is 1 - 3 digits
# can't start with zero
# unless the zero is followed by a period
#then optional (optional comma then 3 digits)
#then optional (period then unlimited digits)
end of line
`;
// 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