node.js - Access Javascript nested objects safely

Question

I have json based data structure with objects containing nested objects. In order to access a particular data element I have been chaining references to object properties together. For example:

var a = b.c.d;

If b or b.c is undefined, this will fail with an error. However, I want to get a value if it exists otherwise just undefined. What is the best way to do this without having to check that every value in the chain exists?

I would like to keep this method as general as possible so I don't have to add huge numbers of helper methods like:

var a = b.getD();

or

var a = helpers.getDFromB(b);

I also want to try to avoid try/catch constructs as this isn't an error so using try/catch seems misplaced. Is that reasonable?

Any ideas?

Answer 1

Standard approach:

var a = b && b.c && b.c.d && b.c.d.e;

is quite fast but not too elegant (especially with longer property names).

Using functions to traverse JavaScipt object properties is neither efficient nor elegant.

Try this instead:

try { var a = b.c.d.e; } catch(e){}

in case you are certain that a was not previously used or

try { var a = b.c.d.e; } catch(e){ a = undefined; }

in case you may have assigned it before.

This is probably even faster that the first option.