What is the usage of typeof in javascript?

Question

typeof returns the primitive data type but I am not getting why it is used in javascript?

Answer 1

I am not getting why it is used in javascript?

typeof is used to

return[s] the primitive data

For example, if I wanted to know if something was undefined, I could do

if (typeof object === 'undefined')

to check because if it is undefined there is no datatype (because it's undefined). This is generally why typeof would be used other than for logging purposes, to see what is received through ajax, or for making functions that accept a parameter that can have different types and checking that type with typeof, etc.

Answer 2

typeof is an unary operator that is placed before a single operand which can be of any type. Its value is a string that specifies the type of operand.

   - x                             typeof x

   undefined                        "undefined"
   null                             "object"
   true or false                    "boolean"
   any number or NaN                "number"
   any string                       "string"
   any function                     "function"
   any non function native object   "object"

The typeof works sufficiently well with primitive values except null.typeof cannot distinguish between null & object because null is falsy & objects are truthy.Here are few case studies which may be useful. typeof evaluates to object for all object and array values other than function.How typeof deals with function is probably beyond the scope of this question.

Hope this will help you.