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

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
– philip yoo, Commented Mar 12, 2017 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". — Emanuele Coppola
– Emanuele Coppola, Commented Mar 12, 2017 at 23:57
@Manu: don't access the property if the variable is empty or doesn't exist. — Felix Kling
– Felix Kling, Commented Mar 13, 2017 at 0:06
For more elegant way of checking nested object properties, you can use a method presented by @georg in here or see this mature post JavaScript test for existence of nested object key — Egel
– Egel, Commented Mar 13, 2017 at 0:25

Dushyant Sabharwal · Accepted Answer · 2017-06-15 15:12:20Z

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, 2017 at 15:12

Dushyant Sabharwal

3554 silver badges15 bronze badges

answered Mar 12, 2017 at 23:59

hola

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6 Comments

Felix Kling Over a year ago

That will still throw an error in the OP's case, since myUnexisistingObject isn't even declared.

hola Over a year ago

I don't think op said that myUnexistingObject wasn't declared.

Felix Kling Over a year ago

But the error they are getting says that.

hola Over a year ago

Okay, I know what you mean, but declared !== defined.

Felix Kling Over a year ago

Sure. I'm just saying that the OP would get exactly the same error with your solution.

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