Is there a standard function to check for null, undefined, or blank variables in JavaScript?

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

if( value ) {}

Would evaluate to true if are not value :

• Null
• Undefined
• NaN
• Empty string ("")
• 0
• False

The above list represents all possible falsy values in Ecma-/javascript. Find it in the Specificationat ToBoolean .

Furthermore, if you don't know whether a variable exists (that means, if it is declared) you should CH Eck with the typeof operator. For instance

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

If you can being sure that a variable are declared at least and you should directly check if it have a truthy value like sh Own above.

Further read:http://typeofnan.blogspot.com/2011/01/typeof-is-fast.html

http://stackoverflow.com/questions/5515310/ is-there-a-standard-function-to-check-for-null-undefined-or-blank-variables-in/5515349#5515349

Is there a standard function to check for null, undefined, or blank variables in JavaScript?