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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 (let 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 (let x in myObj) {
  text = += myObj[x] + ", ";
}
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