json-objects.md

JSON & Objects in JavaScript

Summary

Code	Description	Example
parse	JSON parser	let json = JSON.parse(<json_string>);
stringify	JSON stringifier	let json = JSON.stringify(<json_object>);
obj[] =	Add value	<object>[<new_key>] = <value>;
obj[]	Get value	let value = <object>[<key>];
obj[]	Update value	<object>[<key>] = <value>;
delete	Delete value	delete <object>[<key>];

Difference between JSON and JS objects

• JSON (JavaScript Object Notation) is:

  • a text file with the .json extension
  • a lightweight format for storing and transporting data.
  • a string format that is easy to parse and manipulate.
  • mainly used for sending and receiving data between applications annd servers.

• JS objects are:

  • created with curly brackets ({}) inside a JS file
  • a data structure that is used to store key-value pairs.
  • mainly used for storing data in JavaScript applications.

Example:

// JSON (string format)
/* example.json */
{
  "name": "John",
  "age": 30
  "pets": [
    "cat",
    "dog"
  ]
}

// JS object (key-value pairs)
let jsObject = { name: "John", age: 30, pets: ["cat", "dog"] };

Manipulating JSON

Parse JSON

Use JSON.parse to parse JSON.

let obj = JSON.parse(<json_string>);

<json_string> is the string you want to parse.

Example:

let obj = JSON.parse('{"name": "John", "age": 30}');

console.log(obj); // Output: { name: "John", age: 30 }

Stringify JSON

Use JSON.stringify to stringify JSON.

let json = JSON.stringify(<json_object>);

<json_object> is the object you want to stringify.

Example:

let json = JSON.stringify({ name: "John", age: 30 });

console.log(json); // Output: '{"name":"John","age":30}'

Manipulating JS objects

Add value to an object

Use <object>[<new_key>] = <value> to add value to JSON.

<object>[<new_key>] = <value>

<object> is the object you want to add value to. <new_key> is the new key you want to add value to. <value> is the value you want to add.

Example:

let obj = {
  name: "John",
  age: 30,
};

obj["city"] = "New York";

console.log(obj); // Output: { name: "John", age: 30, city: "New York" }

Get value from an object

Use <object>[<key>] to get value from JSON.

<object>[<key>]

<object> is the object you want to get value from. <key> is the key you want to get value from.

Example:

let obj = {
  name: "John",
  age: 30,
};

console.log(obj.name); // Output: "John"

Update value in an object

Use <object>[<key>] = <value> to update value in JSON.

<object>[<key>] = <value>

<object> is the object you want to update value in. <key> is the key you want to update value in.

Example:

let obj = {
  name: "John",
  age: 30,
};

obj.age = 31;

console.log(obj); // Output: { name: "John", age: 31 }

Delete value from an object

Use delete <object>[<key>] to delete value from JSON.

delete <object>[<key>]

<object> is the object you want to delete value from. <key> is the key you want to delete value from.

Example:

let obj = {
  name: "John",
  age: 30,
};

delete obj.age;

console.log(obj); // Output: { name: "John" }