1. typeOf()
      1.  console.log(typeof (2)); //number
      2.  console.log(typeof ('a')); //string
      3.  console.log(typeof ([])); //object
      4.  console.log(typeof ({})); //object
      5.  console.log(typeof (null)); //object
      6.  console.log(typeof (undefined)); //undefined
      7.  console.log(typeof (NaN)); //number
      8.  console.log(typeof (''));  //string
      9.  console.log(typeof (function () {}));  //function
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