Best approach for determining if an object in reference is null [duplicate]

Question

In JavaScript (or TypeScript), if I'm going to reference something like:

return myObj1.myObj2.myObj3.myProperty;

to be safe, I guard it with something like:

if (myObj1 && myObj2 && myObj3) return myObj1.myObj2.myObj3.myProperty; else return null;

Is there a more concise way of just getting null from the above reference without surrounding it by an if?

Please note, since I'll be using this in a TypeScript app, some solutions may not work with dynamic object definition.

Thanks.

I suppose you mean if (myObj1 && myObj1.myObj2 && myObj1.myObj2.myObj3)? — Sarah Groß
– Sarah Groß, Commented Oct 27, 2017 at 15:01
What if you recursively prints the object is this what you need jsbin.com/xuniluqaqa/edit?js,console,output ? — xsami
– xsami, Commented Oct 27, 2017 at 15:12
@Andreas, your link provided a good answer at stackoverflow.com/a/6491509/1775513. Add as answer and I'll mark it as such. BTW, any idea if there is a performance degradation accessing a property like this? — Michael Witt
– Michael Witt, Commented Oct 27, 2017 at 15:25

Duncan Thacker · Accepted Answer · 2017-10-27 15:04:26Z

I'd use a library like lodash for this:

 //gets undefined if any part of the path doesn't resolve. const answer = _.get(myObj1, "myObj2.myObj3.myProperty"); //gets null if any part of the path doesn't resolve. const answer2 = _.get(myObj1, "myObj2.myObj3.myProperty", null);

See https://lodash.com/docs/4.17.4#get for details.

llama · Accepted Answer · 2017-10-27 15:09:22Z

You can define some temporary objects to substitute when a lookup fails.

return (((myObj1||{}).myObj2||{}).myObj3||{}).myProperty || null;

You can make a reusable object if desired.

const o = Object.create(null);

Then use it as needed.

return (((myObj1||o).myObj2||o).myObj3||o).myProperty || null;

Looks like a good Javascript solution. I didn't take into account that I might need a Typescript only solution because this gives errors because myObj2 does not exist on o (or {}).

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