const regex = /(GSTIN No:-): (.*?\d\s)/gm;
// Alternative syntax using RegExp constructor
// const regex = new RegExp('(GSTIN No:-): (.*?\\d\\s)', 'gm')
const str = `TAX INVOICE CA MANIN DER SINGH AND ASSOCIATES 253 B 1/12 APSARA ARCADE PUSA ROAD.NEW DELHl-110005 GSTIN No 07APAFD8365H1Z9 Bill to Place of Supply INVOICE No Dated RK Electrical Works RK Electrical Works A-240 Palam Vihar, Delhi GSTIN No:-07BBUPS5612K1Z9 Description of Services Professional Services for Month of July Total Less Discount Taxable Value ADDCGST9% ADDSGST9% Total Amount Chargeable (in words) Rupees One Lac Eighteen Thousand Only Company's PAN: AAKFD6723D Note-Please make cheques in favor of "CA Maninder Singh and Associates" A-240 Palam Vihar, Delhi MSA-Tl-02 1-Jul-17 SAC CODE Amount 9982 100000 100000 0 100000 9% 9000 9% 9000 118000.00 For CA Maninder Singh & Associates Authorised Signatory ()-`;
const subst = `$1,$2 in $3:`;
// 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