Is there any easy way to check is null or empty in Javascript?

Question

Is there any standard function available in Javascript to check is null or empty of an variable instead of writing like below

if (val != "" && val != null val != undefined)
{
   x = val;
}

Thanks

Answer 1

The easiest way to check is

if (val){
   x=val;
} 

but if you want to check just for empty string then go for.

if(val != ""){
  x=val;
}

Hope this helps.

Answer 2

If you are using JQuery, then you can use

if(!jQuery.isEmptyObject(val))
{
}

Answer 3

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. Find it in the specification at the ToBoolean section.

Furthermore, if you do not 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.

• Tamara
  Writer