OptionalbodyOptionalcacheA string indicating how the request will interact with the browser's cache to set request's cache.
OptionalcredentialsA string indicating whether credentials will be sent with the request always, never, or only when sent to a same-origin URL. Sets request's credentials.
OptionalheadersA Headers object, an object literal, or an array of two-item arrays to set request's headers.
OptionalintegrityA cryptographic hash of the resource to be fetched by request. Sets request's integrity.
OptionalkeepaliveA boolean to set request's keepalive.
OptionalmethodA string to set request's method.
OptionalmodeA string to indicate whether the request will use CORS, or will be restricted to same-origin URLs. Sets request's mode.
OptionalpriorityOptionalredirectA string indicating whether request follows redirects, results in an error upon encountering a redirect, or returns the redirect (in an opaque fashion). Sets request's redirect.
OptionalreferrerA string whose value is a same-origin URL, "about:client", or the empty string, to set request's referrer.
OptionalreferrerA referrer policy to set request's referrerPolicy.
OptionalsignalAn AbortSignal to set request's signal.
Optionaltimeout请求超时时间（毫秒） 默认：0（表示无超时）
OptionalwindowCan only be null. Used to disassociate request from any Window.
Optionalwith是否携带凭证（cookies、HTTP 认证等）
注意：当使用 XMLHttpRequest 降级时，仅支持 boolean（true/false）
A BodyInit object or null to set request's body.