I am getting the following JavaScript error:
'value' is null or not an object
Can someone please let me know what is the best way to check whether an object's value is NULL in JavaScript as I have been using:
if ((pNonUserID !== "") || (pExtUserID !== "")){
Is this correct or is there a better way?
You don't have to do that:
var n=null;
if(n)alert('Not null.'); // not shown
if(!n)alert('Is null.'); // popup is shown
Your error implies otherwise:
var n=null;
alert(n.something); // Error: n is null or not an object.
In the case above, something like this should be used:
if(n)alert(n.something);
if(!n)alert('Is null.'); will also alert Is null if n == '' or n == 0, and other cases.The !== operator returns true when two variables are not the same object. It doesn't look at the values of the objects at all
To test if something is null:
myVar == null
Your code was testing to see if the variable 'pNonUserId' referred to the same object as "", which can never be true as "" will always be a new instance of the empty string.
As an aside, a test such as:
var n = something();
// do stuff
if (n)
doSomethingElse();
Is a bad idea. If n was a boolean and false, but you were expecting the if block to test nullify you'll be in for a shock.
var n = null; if (n !== null) { doSomething(n); } but alas, a null Object will hapily evaluate to false above. If it was decided to make null an object, and it was decided that "===" should test for type as well as value, then the above should be valid code. Drives me nuts.if (pNonUserID && pExtUserID)
{
// neither pNonUserId nor pExtUserID are null here
}
Any Javascript variable automatically evaluates to true when it references an object.
What you were doing are comparisons to empty strings, which are not the same as null.
null, undefined and empty string is consider as false in conditional statement.
so
if(!n) alert("n is null or undefined or empty string");
if(n) alert("n has some value");
therefor, inflagranti suggested condition will work perfectly for you
if(pNonUserID && pExtUserID) {
}
null. IfpNonUserID = null;then the expression will evaluate totrue. But I think the error message is not related to the code you posted. The error is somewhere else.!=it would have worked (since it checks the value, andnull==""). See my answer for more info.