JSON Object Literals

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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 {}.
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


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};

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Normally, you create a JavaScript object by parsing a JSON string:

Example

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

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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;

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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"];
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Looping an Object
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 + ", ";
}

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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] + ", ";
}

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Reference: https://www.w3schools.com/js/js_json_objects.asp