Is there a universal JavaScript function that checks that a variable has a value and ensures that it's not undefined
or null
? I've got this code, but I'm not sure if it covers all cases:
function isEmpty(val){
return (val === undefined || val == null || val.length <= 0) ? true : false;
}
Best Answer
You can just check if the variable has a
truthy
value or not. That meanswill evaluate to
true
ifvalue
is not:The above list represents all possible
falsy
values in ECMA-/Javascript. Find it in the specification at theToBoolean
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 instanceIf you can be sure that a variable is declared at least, you should directly check if it has a
truthy
value like shown above.