How can i check if an object is undefined (javascript)?

Question

I have to check if a object is undefined but when i do

typeof myUnexistingObject.myUnexistingValue == 'undefined'

i get this error

Uncaught ReferenceError: myUnexistingObject is not defined

so, how can I check for undefined obects or properties?

Since the object is undefined, you first need to check if the object is defined before checking the value — philip yoo, Mar 12 '17 at 23:53
Hmm i tried to check the undefined object, if it is not undefined i have to check if it has some undefined values but i got an error, " Cannot read property 'original' of undefined". — Manu, Mar 12 '17 at 23:57
@Manu: don't access the property if the variable is empty or doesn't exist. — Felix Kling, Mar 13 '17 at 00:06
For more elegant way of **checking nested object properties**, you can use a method presented by @georg in **[here](http://stackoverflow.com/a/23809123/1977012)** or see this mature post **[JavaScript test for existence of nested object key](http://stackoverflow.com/q/2631001/1977012)** — Egel, Mar 13 '17 at 00:25

score 3 · Accepted Answer · edited Jun 15 '17 at 15:12

3

You must check for each potentially defined property before using it:

function checkUnexistingObject(myUnexistingObject) {
  if (myUnexistingObject !== undefined) {
    if (myUnexistingObject.otherObject !== undefined) {
      console.log("All is well");
    }
  }
}
checkUnexistingObject({});
checkUnexistingObject({otherObject: "hey"});

edited Jun 15 '17 at 15:12

Dushyant Sabharwal

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answered Mar 12 '17 at 23:59

hola

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That will still throw an error in the OP's case, since `myUnexisistingObject` isn't even declared. – Felix Kling Mar 13 '17 at 00:02
I don't think op said that myUnexistingObject wasn't declared. – hola Mar 13 '17 at 00:18
1

But the error they are getting says that. – Felix Kling Mar 13 '17 at 00:22
Okay, I know what you mean, but declared !== defined. – hola Mar 13 '17 at 00:26
2

Sure. I'm just saying that the OP would get exactly the same error with your solution. – Felix Kling Mar 13 '17 at 00:27
Ah, I see. You're right, my bad. – hola Mar 13 '17 at 02:11

How can i check if an object is undefined (javascript)?

1 Answers1