javascript null undefined

You can just check if the variable has a truthy value or not. That means

if( value ) {
}

will evaluate to true if value is not:

  • null
  • undefined
  • NaN
  • empty string (“”)
  • 0
  • false

The above list represents all possible falsy values in ECMA-/Javascript. Furthermore, if you don’t know whether a variable exists (that means, if it was declared) you should check with the typeof operator. For instance

if( typeof foo !== 'undefined' ) {
    // foo could get resolved and it's defined
}

If you can be sure that a variable is declared at least, you should directly check if it has a truthy value like shown above.

http://stackoverflow.com/questions/154059/what-is-the-best-way-to-check-for-an-empty-string-in-javascript

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About rahul23134654

Hi, I am Rahul Meha , B.E. in (I.T.)
This entry was posted in UI Js and tagged . Bookmark the permalink.

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