The json() method of the Response interface takes a Response stream and reads it to completion. It returns a promise which resolves with the result of parsing the body text as JSON.

Note that despite the method being named json(), the result is not JSON but is instead the result of taking JSON as input and parsing it to produce a JavaScript object.

None.

A Promise that resolves to a JavaScript object. This object could be anything that can be represented by JSON — an object, an array, a string, a number…

In our fetch JSON example (run fetch JSON live), we create a new request using the Request() constructor, then use it to fetch a .json file. When the fetch is successful, we read and parse the data using json(), then read values out of the resulting objects as you'd expect and insert them into list items to display our product data.

const myList = document.querySelector("ul");
const myRequest = new Request("products.json");

fetch(myRequest)
  .then((response) => response.json())
  .then((data) => {
    for (const product of data.products) {
      const listItem = document.createElement("li");
      listItem.appendChild(document.createElement("strong")).textContent =
        product.Name;
      listItem.append(` can be found in ${product.Location}. Cost: `);
      listItem.appendChild(
        document.createElement("strong"),
      ).textContent = `£${product.Price}`;
      myList.appendChild(listItem);
    }
  })
  .catch(console.error);

• ServiceWorker API
• Cross-Origin Resource Sharing (CORS)
• HTTP