With JSON.stringify() found in json2.js or native in most modern browsers.

JSON.stringify(value, replacer, space)
    value       any JavaScript value, usually an object or array.
    replacer    an optional parameter that determines how object
                values are stringified for objects. It can be a
                function or an array of strings.
    space       an optional parameter that specifies the indentation
                of nested structures. If it is omitted, the text will
                be packed without extra whitespace. If it is a number,
                it will specify the number of spaces to indent at each
                level. If it is a string (such as "\t" or " "),
                it contains the characters used to indent at each level.

A common use of JSON is to exchange data to/from a web server. When receiving data from a web server, the data is always a string. Parse the data with JSON.parse(), and the data becomes a JavaScript object.

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

The jQuery method is now deprecated. Use this method instead:

let jsonObject = JSON.parse(jsonString);

Original answer using deprecated jQuery functionality:

If you're using jQuery just use:

jQuery.parseJSON( jsonString );

It's exactly what you're looking for (see the jQuery documentation).