JSON Objects

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JSON Objects

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 contained by curly braces {}.

JSON object literals consist of key/value pairs.

Keys and values are separated by a colon.

Keys must be strings, and values should 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. As soon it is converted to a JavaScript variable, it becomes a JavaScript object.

JavaScript Objects

Create a JavaScript object from a JSON object literal:

Example

<!DOCTYPE html>

<html>

<body>

<h2>Creating an Object from a JSON Literal</h2>

<p id=”demo”></p>

<script>

const myObj = {“name”:”John”, “age”:30, “car”:null};

document.getElementById(“demo”).innerHTML = myObj.name;

</script>

</body>

</html>

Output

Creating an Object from a JSON Literal

John

normally, you create a JavaScript object by parsing a JSON string.

Example

<!DOCTYPE html>

<html>

<body>

<h2>Creating an Object Parsing JSON</h2>

<p id=”demo”></p>

<script>

const myJSON = ‘{“name”:”John”, “age”:30, “car”:null}’;

const myObj = JSON.parse(myJSON);

document.getElementById(“demo”).innerHTML = myObj.name;

</script>

</body>

</html>

Output

Creating an Object Parsing JSON

John

Accessing Object Values

Access the object values by using dot (.) notation:

Example

<!DOCTYPE html>

<html>

<body>

<h2>Access a JavaScript Object</h2>

<p id=”demo”></p>

<script>

const myJSON = ‘{“name”:”John”, “age”:30, “car”:null}’;

const myObj = JSON.parse(myJSON);

document.getElementById(“demo”).innerHTML = myObj.name;

</script>

</body>

</html>

Output

Access a JavaScript Object

John

Accessing the object values by using bracket ([]) notation.

Example

<!DOCTYPE html>

<html>

<body>

<h2>Access a JavaScript Object</h2>

<p id=”demo”></p>

<script>

const myJSON = ‘{“name”:”John”, “age”:30, “car”:null}’;

const myObj = JSON.parse(myJSON);

document.getElementById(“demo”).innerHTML = myObj[“name”];

</script>

</body>

</html>

Output

Access a JavaScript Object

John

Looping an Object

Loop through object properties with a for-in loop.

Example

<!DOCTYPE html>

<html>

<body>

<h2>Looping Object Properties</h2>

<p id=”demo”></p>

<script>

const myJSON = ‘{“name”:”John”, “age”:30, “car”:null}’;

const myObj = JSON.parse(myJSON);

let text = “”;

for (const x in myObj) {

  text += x + “, “;

}

document.getElementById(“demo”).innerHTML = text;

</script>

</body>

</html>

Output

Looping Object Properties

name, age, car,

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

Example

<!DOCTYPE html>

<html>

<body>

<h2>Looping JavaScript Object Values</h2>

<p id=”demo”></p>

<script>

const myJSON = ‘{“name”:”John”, “age”:30, “car”:null}’;

const myObj = JSON.parse(myJSON);

let text = “”;

for (const x in myObj) {

  text += myObj[x] + “, “;

}

document.getElementById(“demo”).innerHTML = text;

</script>

</body>

</html>

Output

Looping JavaScript Object Values

John, 30, null,


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