Most efficient Javascript way to check if an object within an unknown object exists [duplicate]

Answer 1

It's not nice in JavaScript.

You could add them to one big condition...

if (obj.prop && obj.prop.someOtherProp) { }

...or write a helper function where you pass an object and a string...

var isPropSet = function(object, propPath) {
    return !! propPath.split('.')
           .reduce(function(object, prop) { return object[prop] || {}; }, object);
};

isPropSet(obj, 'prop.someOtherProp);

...or you could use CoffeeScript and its ? operator...

obj.prop?.someOtherProp

You could also wrap the lookup in a try/catch, but I wouldn't recommend it.