What Is The Issue In This Javascript Short Circuit Assignment

the following javascript code is getting giving undefined as the final output. But as far as I know the OR ' || ' operator will stop the evaluation as soon as it gets 'true'. But i

Solution 1:

In one word: operator precedence.

Yes, || short-circuits and doesn't evaluate the second half of the expression used as condition in the ternary operator.

field.ipaddr || (field.ip6addr && field.ip6addr != '::') ? .. : ..

Evaluates to:

'0.0.0.0' ? .. : ..

Which evaluates to true and then evaluates the true branch of the ternary operator:

field.ip6addr

If you want a different logical grouping, use parentheses:

field.ipaddr || (.. ? .. : ..);

Solution 2:

I'm assuming you know that you've written field.ipaddr instead of fields.ipaddr. Probably for testing purposes. If the last part of the expression is your problem, write it like so:

(undefined || fields.sysid);

Solution 3:

I don't think so is there any property with name ip6addr in current object?

var bestName = (field.ipaddr || (field.ip6addr && field.ip6addr != '::') ? field.ipaddr : undefined || field.sysid);
undefined

Either you should add ip6addr in current object or replace with appropriate property