bugl
bugl
HomeLearnPatternsSearch
HomeLearnPatternsSearch

Loading lesson path

Learn/JavaScript/Objects, Classes, and Advanced Patterns
JavaScript•Objects, Classes, and Advanced Patterns

JSON Object Literals

This is a JSON string:

'{"name":"John", "age":30, "car":null}'

Inside the JSON string there is a JSON object literal:

{"name":"John", "age":30, "car":null}
JSON object literals are surrounded by curly braces {}.

Formula

JSON object literals contains key/value pairs.

Keys and values are separated by a colon. Keys must be strings, and values must be a valid JSON data type: string number object array boolean null

Formula

Each key/value pair is separated by a comma.

It is a common mistake to call a JSON object literal "a JSON object". JSON cannot be an object. JSON is a string format. The data is only JSON when it is in a string format. When it is converted to a JavaScript variable, it becomes a JavaScript object.

JavaScript Objects

You can create a JavaScript object from a JSON object literal:

Example myObj = {"name":"John", "age":30, "car":null}; Normally, you create a JavaScript object by parsing a JSON string:

Example myJSON = '{"name":"John", "age":30, "car":null}';

myObj = JSON.parse(myJSON);

Accessing Object Values

You can access object values by using dot (.) notation:

Example

const myJSON = '{"name":"John", "age":30, "car":null}';
const myObj = JSON.parse(myJSON);
x = myObj.name;
You can also access object values by using bracket ([]) notation:

Example

const myJSON = '{"name":"John", "age":30, "car":null}';
const myObj = JSON.parse(myJSON);
x = myObj["name"];

Looping an Object

Formula

You can loop through object properties with a for - in loop:

Example

const myJSON = '{"name":"John", "age":30, "car":null}';
const myObj = JSON.parse(myJSON);
let text = "";
for (const x in myObj) {
text += x + ", ";
}

Formula

In a for - in loop, use the bracket notation to access the property values

Example

const myJSON = '{"name":"John", "age":30, "car":null}';
const myObj = JSON.parse(myJSON);
let text = "";
for (const x in myObj) {
text += myObj[x] + ", ";
}

Previous

JSON.stringify()

Next

JSON Array Literals