Headers and Mode

Headers

The headers attribute is used to add more information about the resource being fetched or the client doing the fetching. A Headers object can be created using the new Headers() constructor and individual headers can be added to the Headers object through the **append() method.

Notice how a new Headers object is created and assigned to the headers attribute of the init object:

let myHeaders = new Headers();
    myHeaders.append('Content-Type', 'application/json');

let initObject = {
    headers: myHeaders
}

Mode

The mode attribute is a string that is used to determine whether or not the Fetch request can fetch resources from different servers.

In this course we will cover the following two mode types:

• same-origin - the Fetch request can only fetch resources from the same server
• cors (cross origin HTTP request) - the Fetch request can fetch resources from different servers

Notice how an init object is created with a mode attribute set to 'cors':

let initObject = {
    mode: 'cors'
}