JavaScript: response.json()

The response.json() method parses a JSON response body into a JavaScript object or array.

What you will learn

How response.json() converts a JSON body
How to return its Promise to the next .then()
How to handle invalid JSON or network failures with .catch()

Minimal example

fetch("data.json")
  .then(response => {
    if (!response.ok) throw new Error(`HTTP ${response.status}`);
    return response.json();
  })
  .then(data => {
    console.log("Parsed data:", data);
  })
  .catch(error => {
    console.error("Could not read JSON:", error);
  });

response.json() returns a Promise because reading and parsing the body takes time. Returning it makes the parsed object or array available to the next callback.

Important points

The response body must contain valid JSON, or parsing rejects the returned Promise.
Check response.ok before parsing when HTTP errors should be handled explicitly.
A response body is normally consumed once; choose json() or text() based on the format you need.