Check if javascript object/property is defined

Question

So i've read a handful of SO posts and some blogs, but still can't figure out why my code isn't working.

My code:

function myFunct(d) {
    if (typeof d.parent.name == "undefined") {
        console.log("undefined") ;} else { console.log("defined") ;}
    }

d is an object that looks something like:

Object { 
children: Object, 
count: 676
}

I've tried using (!d.parent.name), hasOwnProperty, ===, and as above using typeof. Any suggestions?

The error I recieve is TypeError: d.parent.name is undefined

UPDATE:

Ok thanks everyone for the input, and my apologies if the question was confusing. I was actually looking for d.parent.parent but tried to simplify the question by using d.parent. I think the problem is that d.parent is not defined so it doesn't even get to d.parent.parent. Sorry for not being more specific!

typeof Object === 'undefined' is a valid way to use typeof — NickSlash
– NickSlash, Commented Apr 11, 2016 at 21:17
@NickSlash Thanks, unfortunately I still get the same TypeError — As3adTintin
– As3adTintin, Commented Apr 11, 2016 at 21:18
can you give this a try? if (d.parent && typeof d.parent.name === 'undefined') — NickSlash
– NickSlash, Commented Apr 11, 2016 at 21:20

JellyRaptor · Accepted Answer · 2017-04-25 19:43:23Z

5

If you want an undefined-safe check all the way down your object tree, you can use:

if( typeof( ((d || {}).parent || {}).name ) === 'undefined') {

}

If you have the luxury of having Lodash at your disposal:

var d = { 
     parent: {
          name: "Joe"
     }
};

if ( typeof (_.get(d, "parent.name")) === 'undefined' ) {

}

edited Apr 25, 2017 at 19:43

answered Apr 11, 2016 at 22:11

JellyRaptor

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Comments

isvforall · Accepted Answer · 2016-04-11 21:31:22Z

4

Try to check all children with logical OR

if (typeof d == "undefined" ||
    typeof d.parent == "undefined" ||
    typeof d.parent.name == "undefined") {
// ...
}

edited Apr 11, 2016 at 21:31

answered Apr 11, 2016 at 21:15

isvforall

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2 Comments

As3adTintin Over a year ago

Gah I get the same error... I must really be doing something wrong. Thanks though for the suggestions!

ForceMagic Over a year ago

Append typeof d == "undefined" || to the beginning of the if condition

labago · Accepted Answer · 2016-04-11 21:15:25Z

1

if(typeof x === 'undefined')

Use this, it checks for type as well as value, thats what you need.

answered Apr 11, 2016 at 21:15

labago

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5 Comments

As3adTintin Over a year ago

Thanks for the input, however I still receive the same error

ForceMagic Over a year ago

Are you sure you're referencing to an existing value?

labago Over a year ago

Ya @As3adTintin, if for some reason d.parent itself is undefined, the script will error out before it even gets to checking d.parent.name, be aware of that

ForceMagic Over a year ago

True, why don't you first check if the parent is undefined?

As3adTintin Over a year ago

@jlane09 thanks for the feedback. I receive the same error weather I check for d.parent or d.parent.name

user5066707 · Accepted Answer · 2016-04-11 21:32:29Z

0

I believe the error is the property identifier parent. Are you sure your object has the property? The identifier d may be invalid because parent doesn't exists.

answered Apr 11, 2016 at 21:32

user5066707

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