There are two ways to access properties of objects:
var obj = {a: 'foo', b: 'bar'};
obj.a //foo
obj['b'] //bar
Or, if you need to dynamically do it:
var key = 'b';
obj[key] //bar
If you don't already have it as an object, you'll need to convert it.
For a more complex example, let's assume you have an array of objects that represent users:
var users = [{name: 'Corbin', age: 20, favoriteFoods: ['ice cream', 'pizza']},
{name: 'John', age: 25, favoriteFoods: ['ice cream', 'skittle']}];
To access the age property of the second user, you would use users[1].age. To access the second "favoriteFood" of the first user, you'd use users[0].favoriteFoods[2].
Another example: obj[2].key[3]["some key"]
That would access the 3rd element of an array named 2. Then, it would access 'key' in that array, go to the third element of that, and then access the property name some key.
As Amadan noted, it might be worth also discussing how to loop over different structures.
To loop over an array, you can use a simple for loop:
var arr = ['a', 'b', 'c'],
i;
for (i = 0; i < arr.length; ++i) {
console.log(arr[i]);
}
To loop over an object is a bit more complicated. In the case that you're absolutely positive that the object is a plain object, you can use a plain for (x in obj) { } loop, but it's a lot safer to add in a hasOwnProperty check. This is necessary in situations where you cannot verify that the object does not have inherited properties. (It also future proofs the code a bit.)
var user = {name: 'Corbin', age: 20, location: 'USA'},
key;
for (key in user) {
if (user.hasOwnProperty(key)) {
console.log(key + " = " + user[key]);
}
}
(Note that I've assumed whatever JS implementation you're using has console.log. If not, you could use alert or some kind of DOM manipulation instead.)
