How to check 'undefined' value in jQuery

Question

Possible Duplicate:
Detecting an undefined object property in JavaScript
javascript undefined compare

H

Answer 1

I am not sure it is the best solution, but it works fine:

if($someObject['length']!=0){
    //do someting
}

Answer 2

if (value === undefined) {
    // ...
}

Answer 3

In this case you can use a === undefined comparison: if(val === undefined)

This works because val always exists (it's a function argument).

If you wanted to test an arbitrary variable that is not an argument, i.e. might not be defined at all, you'd have to use if(typeof val === 'undefined') to avoid an exception in case val didn't exist.

Answer 4

Note that typeof always returns a string, and doesn't generate an error if the variable doesn't exist at all.

function A(val){
  if(typeof(val)  === "undefined") 
    //do this
  else
   //do this
}

Answer 5

I know I am late to answer the function but jquery have a in build function to do this

if(jQuery.type(val) === "undefined"){
    //Some code goes here
}

Refer jquery API document of jquery.type https://api.jquery.com/jQuery.type/ for the same.