[JS] 取得 unix timestamp 的方法

const timestamp1 = Date.now();
const timestamp2 = new Date().getTime();
const timestamp3 = +new Date();
// 以上三種寫法會取得目前的 unix timestamp
console.log(timestamp1 + " " + timestamp2 + " " + timestamp3);
      
const timestamp4 = new Date('2012-06-08').getTime();
const timestamp5 = +new Date('2012-06-08');
// 以上二種寫法會取得特定日期的 unix timestamp
console.log(timestamp4 + " " + timestamp5);