在JavaScript中的python hasattr？

Question

in javascript:

d={one: false, two: true}
d.one
d.two
d.three

I want to be able to differentiate between d.one and d.three. By default they both evaluate to false, but in my case they should not be treated the same.

Answer 1

You can do

"one" in d // or "two", etc

or

d.hasOwnProperty("one")

You probably want hasOwnProperty as the in operator will also return true if the property is on the an object in the prototype chain. eg.

"toString" in d // -> true

d.hasOwnProperty("toString") // -> false