Fetch API
Setting headers
Request headers give the server information about the request: for example, the Content-Type header tells the server the format of the request's body.
To set request headers, assign them to the headers option.
You can pass an object literal here containing header-name: header-value properties:
const response = await fetch('https://example.org/post', {
headers: {
'Content-Type': 'application/json',
},
// ...
});
Alternatively, you can construct a Headers object, add headers to that object using Headers.append(), then assign the Headers object to the headers option:
const myHeaders = new Headers();
myHeaders.append("Content-Type", "application/json");
const response = await fetch("https://example.org/post", {
headers: myHeaders,
// ...
});
Many headers are set automatically by the browser and can't be set by a script: these are called Forbidden header names. If the mode option is set to no-cors, then the set of permitted headers is further restricted.