Ari Ari - 1 year ago 25
Javascript Question

How to avoid 'cannot read property of undefined' errors?

In my code, I deal with an array that has some entries with many objects nested inside one another, where as some do not. It looks something like the following:

// where this array is hundreds of entries long, with a mix
// of the two examples given
var test = [{'a':{'b':{'c':"foo"}}}, {'a': "bar"}];

This is giving me problems because I need to iterate through the array at times, and the inconsistency is throwing me errors like so:

for (i=0; i<test.length; i++) {
// ok on i==0, but 'cannot read property of undefined' on i==1

I am aware that I can say
if(a.b){ console.log(a.b.c)}
, but this is extraordinarily tedious in cases where there are up to 5 or 6 objects nested within one another. Is there any other (easier) way that I can have it ONLY do the console.log if it exists, but without throwing an error?


What you are doing raises an exception and logically so.

You can always do


But I wouldn't, instead think of your use case.

Why are you accessing data, 6 levels nested that you are unfamiliar of? What use case justifies this?

Usually, you'd like to actually validate what sort of object you're dealing with.

Also, on a side node you should not use statements like if(a.b) because it will return false if a.b is 0 or even if it is "0". Instead check if a.b !== undefined