Question

Hi I’m very new to JS.

Lets say I have an object named test which doesn’t have a property missing. But I try to access the same:

test.missing //getting undefined as output

Now I’m trying to access the missing properties ( like this test.missing.404 ) which will give me a TypeError. But my book says we can get rid of this TypeError by like this:

test.missing && test.missing.404

Now my big question is how one can do a && against the undefined type and TypeError type. Couldn’t able to guess what Js is doing here.

Thanks in advance.

Answer 1

undefined in js is treated as false and if something has value it is treated as true, so:

//if test.missing is NOT undefined and test.missing.404 is also NOT undefined
if (test.missing && test.missing.404)