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JavaScript JSON APIs

Learn how to serialize and parse data strings. Master the transport layer for APIs and browser storage formats.

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Tutor:JSON stands for JavaScript Object Notation. It's a standard text-based format for representing structured data. Even though it originated from JavaScript, it is completely language-independent. APIs heavily rely on it.


Skill Matrix

UNLOCK NODES BY MASTERING JSON METHODS.

Concept: Strict Syntax

JSON requires double quotes around ALL keys. No trailing commas, and no undefined/function values.

System Check

Which of the following is completely valid JSON?

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JavaScript & JSON

Author

Pascual Vila

Frontend Instructor // Code Syllabus

JSON (JavaScript Object Notation) is a lightweight data-interchange format. It is easy for humans to read and write, and easy for machines to parse and generate.

The Rules of JSON

Although JSON is derived from JavaScript object literal syntax, it is highly strict:

  • Property names MUST be enclosed in double quotes. "name": "Alex" is valid, but name: "Alex" is not.
  • Values must be a string, number, object, array, boolean, or null.
  • Functions, Dates, and undefined are NOT supported.
  • Trailing commas are strictly forbidden.

JSON.stringify()

When sending data to a web server, the data has to be a string. We convert a native JavaScript object into a string with JSON.stringify().

const obj = { name: "Alex", age: 30 };
const myJSON = JSON.stringify(obj);

// myJSON is now '{"name":"Alex","age":30}'

JSON.parse()

When receiving data from a web server, the data is always a string. Parse the data with JSON.parse(), and the data becomes a JavaScript object.

const jsonString = '{"name":"Alex","age":30}';
const myObj = JSON.parse(jsonString);

console.log(myObj.name); // Output: Alex
View Bonus Trick: Deep Copy+

Because `JSON.stringify` converts an object completely into a string, and `JSON.parse` creates a brand new object from that string, combining both is a common 'hack' to create a Deep Copy of an object, severing all nested references!


const deepCopy = JSON.parse(JSON.stringify(originalObject));

JSON Glossary

JSON

JavaScript Object Notation. A standard text-based format for representing structured data.

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JSON.stringify()

A method that converts a JavaScript object or value to a JSON string. Often used for sending data to a server.

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JSON.parse()

A method that parses a JSON string, constructing the JavaScript value or object described by the string.

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Serialization

The process of translating a data structure or object state into a format that can be stored or transmitted (e.g., Object to String).

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Deserialization

The process of extracting a data structure from a series of bytes or string (e.g., String to Object).

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SyntaxError

An error thrown when the JS engine encounters tokens or token order that does not conform to the syntax of the language (like invalid JSON).

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