Best approach for determining if an object in reference is null

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)`? — Constantin Groß, Oct 27 '17 at 15:01
[Accessing nested JavaScript objects with string key](https://stackoverflow.com/questions/6491463/accessing-nested-javascript-objects-with-string-key) — Andreas, Oct 27 '17 at 15:03
What if you recursively prints the object is this what you need http://jsbin.com/xuniluqaqa/edit?js,console,output ? — xsami, Oct 27 '17 at 15:12
@Andreas, your link provided a good answer at https://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, Oct 27 '17 at 15:25

llama · Answer 1 · 2017-10-27T15:09:22.997

1

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;

edited Oct 27 '17 at 15:09

answered Oct 27 '17 at 15:04

llama

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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 {}). – Michael Witt Oct 27 '17 at 15:13

score 1 · Answer 2 · answered Oct 27 '17 at 15:04

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.

Best approach for determining if an object in reference is null

2 Answers2