how to convert a time into unix in javascript code example

Example 1: unix time to date javascript

const unixTime = 1210981217;
const date = new Date(unixTime*1000);
console.log(date.toLocaleDateString("en-US"));
//expected: "5/16/2008"

Example 2: javasctipt unix timestamp from date

Math.round(new Date().getTime() / 1000).toString()