epoch date convert in javascript

 epoch date is generally in seconds and milliseconds.

sample:   /Date(1665424800000)/

javascript code to convert in readable date:  

var lsad = String(LoanSanctionApproveDate);

        var lsadUnixDate = lsad.slice(6, 19);

        var lsadToInt = parseInt(lsadUnixDate);

        var loanSancAprvDate = new Date(lsadToInt).toLocaleDateString('es-CL');