How can I replace a variable name by it's content in JS? [duplicate]

This question already has an answer here:

• Dynamically access object property using variable 7 answers

I'm trying to get a JSON object's value like that:

obj = {"name": "abdou", "age": 23}

I know I can access to the value "abdou" by obj.name but assuming that I have a variable that hold the "name" like that:

key = "name"

So my question is how can I access to "abdou" using the variable key I tried

obj.key

but I think it's looking for a "key" value in the JSON object and replied with undefined.

Thank you.

via stodi