const regex = /(..\..).+\n(?<!not )undefined.+/;
// Alternative syntax using RegExp constructor
// const regex = new RegExp('(..\\..).+\\n(?<!not )undefined.+', '')
const str = `datetime,n_dayAVG,n_nightAVG
2021-02-13T23:00:00Z,0,38.75689941512687
2021-02-14T06:00:00Z,42.928258741926456,39.480753102759024
2021-02-15T06:00:00Z,43.75857849703471,39.9099923987705
2021-02-16T06:00:00Z,40.64147976311876,39.62856460216651
2021-02-17T06:00:00Z,43.01380733014874,39.58893298143956
undefined,0,0`;
// Reset `lastIndex` if this regex is defined globally
// regex.lastIndex = 0;
let m;
if ((m = regex.exec(str)) !== null) {
// 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