Let's asume that I have an object:
var obj = {"A":"a", "B":"b", "x":"y", "a":"b"} When I want to refer to "A" I just write obj.A
How to do it when I have key in a variable, i.e.:
var key = "A"; Is there any function that returns a value or null (if key isn't in the object)?
Use bracket notation, like this:
var key = "A"; var value = json[key]; In JavaScript these two are equivalent:
object.Property object["Property"]; And just to be clear, this isn't JSON specific, JSON is just a specific subset of object notation...this works on any JavaScript object. The result will be undefined if it's not in the object, you can try all of this here.
object["Property"] is safer. OTOH, object.Property has the advantage (when Property is known statically) that tools like JSLint can run checks on them.How about:
json[key] Try:
json.hasOwnProperty(key) for the second part of your question (see Checking if a key exists in a JavaScript object?)
