How to check for Undefined?

Question

JavaScript

How to make a check for undefined so that the program is not cut off with a warning?

Tried to do so

var o = {
        	action: getRandomItems
        }
if(typeof o.children !== undefined){

}

So

var o = {
        	action: getRandomItems
        }
if(!!o.children){

}

In any case, I get

UnhandledPromiseRejectionWarning: TypeError: Cannot read property 'children' of undefined

Answer 1

Learn to read mistakes. It says here that undefinedthe object you are trying to read childrenfrom, and not yourself children. In your examples (which, of course, work without problems) in its place is o.