Here is the code:
if(!typeOf(node.parentNode)) return null;
Here is the error:
Uncaught TypeError: Cannot read property 'parentNode' of null
I am trying to test if it is null/undefined/false. But it keeps sending me errors.
How can I test it without getting an error with the if statement?
Test the object reference too:
if (!node || !node.parentNode) return null;
If "node" can really be anything (like, a string or a number in addition to an object reference), you'd also want to test the type.
As the other answers mentioned, your particular errors come from the fact that your node object is actually null. The most bullet-proof way of testing if node.parentNode exists and is not null is:
if ((typeof node==='undefined') || !node || !node.parentNode) return null;
This covers the following cases:
node variable doesn't existnode variable is null or undefinedparentNode is falsy (undefined, null, false, 0, NaN, or '')As per Blue Skies' comments, you should take care about the first check (typeof node === 'undefined') because it masks undeclared variables which may lead to problems later on:
function f() {
if (typeof node==='undefined') {
node = {}; // global variable node, usually not what you want
}
}
node variable doesn't exist, you should allow the error so that it can be properly declared. The reason is that if it wasn't declared, and there's an assignment somewhere else, it'll create an implicit global. So it's better to get the ReferenceError so you can fix it rather than using typeof to hide it.
You have to check to see if node is null first.
if(!node || !node.parentNode) {
return null;
}
This is also known as a "short-circuit" evaluation. When it sees that !node is true, it will immediately execute what is inside the block because the operator is an OR (||) and in an OR if one of the inputs is true, then the result can only be true.
Also, typeof is a keyword; not a function (although your code will still work).
undefined as well.
null check, but I see your point.try {
if (!typeOf(node.parentNode)) return null;
} catch (err) {
console.log(err);
}
