The standard way to parse JSON in JavaScript is JSON.parse()

The JSON API was introduced with ES5 (2011) and has since been implemented in >99% of browsers by market share, and Node.js. Its usage is simple:

const json = '{ "fruit": "pineapple", "fingers": 10 }';
const obj = JSON.parse(json);
console.log(obj.fruit, obj.fingers);

The only time you won't be able to use JSON.parse() is if you are programming for an ancient browser, such as IE 7 (2006), IE 6 (2001), Firefox 3 (2008), Safari 3.x (2009), etc. Alternatively, you may be in an esoteric JavaScript environment that doesn't include the standard APIs. In these cases, use json2.js, the reference implementation of JSON written by Douglas Crockford, the inventor of JSON. That library will provide an implementation of JSON.parse().

When processing extremely large JSON files, JSON.parse() may choke because of its synchronous nature and design. To resolve this, the JSON website recommends third-party libraries such as Oboe.js and clarinet, which provide streaming JSON parsing.

jQuery once had a $.parseJSON() function, but it was deprecated with jQuery 3.0. In any case, for a long time, it was nothing more than a wrapper around JSON.parse().

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.)

You can simply use JSON.parse.

The definition of the JSON object is part of the ECMAScript 5 specification. node.js is built on Google Chrome's V8 engine, which adheres to ECMA standard. Therefore, node.js also has a global object JSON^[docs].

Note - JSON.parse can tie up the current thread because it is a synchronous method. So if you are planning to parse big JSON objects use a streaming json parser.