In order to consolidate the foundation, I will be described in detail by way of example, let us get to know typeof and instanceof.
<!DOCTYPE html> <html lang="en"> <head> <meta charset="UTF-8"> <meta name="viewport" content="width=device-width, initial-scale=1.0"> <meta http-equiv="X-UA-Compatible" content="ie=edge"> <title>Document</title> </head> <body> <script> console.log( 'typeof 123', ':', typeof 123 ); // number console.log( "typeof 'str'", ':', typeof 'str' ); // string console.log( "typeof !'0'", ':', typeof !'0' ); // boolean console.log( "typeof new Function()", ':', typeof new Function() ); // function console.log( 'typeof myname', ':', typeof myname ); // undefined console.log( 'typeof null', ':', typeof null ); // object console.log( "typeof {name: 'hello'}", ':', typeof {name: 'hello'} ); // object console.log( "typeof [1,2,3]", ':', typeof [1,2,3] ); // object console.log( "[1,2] instanceof Array", ':', [1,2] instanceof Array ); // true console.log( "Array.isArray([1,2])", ':', Array.isArray([1,2]) ); // true console.log( "({name: 'he'}) instanceof Object", ':', ({name: 'he'}) instanceof Object ); // true console.log( "new Date() instanceof Date", ':', new Date() instanceof Date ); function Person(){} the console.log ( new new the Person () the instanceof the Person); // to true // Next inherit function the Parent () {}; function Child () {}; function Other () {}; Child.prototype = new Parent(); let child = new Child(); the console.log (Child the instanceof Child); // to true the console.log (Child the instanceof the Parent); // to true the console.log (Child the instanceof Object); // to true the console.log (Child the instanceof Other); // to false Console. log (Parent.prototype .__ proto__ === Object.prototype); // to true // the instanceof can only be used to determine whether two objects belonging to the instance relation, but can not determine what type of a specific object instance belongs. function Fun () {} console.log(typeof fun); // function console.log(fun instanceof Function); // true console.log(fun instanceof Object); // true </script> </body> </html>