Typeof /regex / = 'object ' // See Regular expressions section for historical results // The following are confusing, dangerous, and wasteful.

use Array.isArray or // to differentiate regular objects from arrays typeof = 'object ' Typeof undeclaredVariable = 'undefined ' Typeof declaredButUndefinedVariable = 'undefined ' iterator = 'symbol ' // Undefined typeof undefined = 'undefined ' Typeof Boolean( 1) = 'boolean ' // Boolean() will convert values based on if they're truthy or falsy typeof !!( 1) = 'boolean ' // two calls of the ! (logical NOT) operator are equivalent to Boolean() // Symbols typeof Symbol() = 'symbol ' typeof Symbol( 'foo ') = 'symbol ' typeof Symbol.

Typeof '1 ' = 'string ' // note that a number within a string is still typeof string typeof ( typeof 1) = 'string ' // typeof always returns a string typeof String( 1) = 'string ' // String converts anything into a string, safer than toString // Booleans typeof true = 'boolean ' Typeof NaN = 'number ' // Despite being 'Not-A-Number' typeof Number( '1 ') = 'number ' // Number tries to parse things into numbers // Strings typeof ' ' = 'string '

Js typeof object