The high-level web standard fetch() API and the low-level ECMA-419 embedded standard HTTP Client APIs are both available to Embedded JavaScript developers using the Moddable SDK. In fact, fetch() is implemented using the HTTP Client.

Note: There are two versions of fetch(). The default is the smaller of the two, without support for streams.

• Make Request
• Make Secure Request
• Send Request Headers
• Receive Response Headers
• Send Request Body

• Make Request
• Make Secure Request
• Send Request Headers
• Receive Response Headers
• Send Request Body

If fetch() works for your project, you should use it. You can always start with fetch() and switch to HTTP Client later. With fetch() you'll usually write less code. Because fetch() is a well-known web standard, many developers are already familiar with it.

Situations where fetch() might not be the best choice include when resources like RAM and ROM are very constrained and when you need precise control over the buffering of request and response bodies.

Using HTTP Client requires more code and a deeper understanding of the HTTP protocol. But, it offers real advantages:

• Lower runtime overhead
• Stream request body
• Stream response body
• Ignore unneeded response headers
• Smaller firmware size

Include the fetch() manifest in your project's manifest.json:

$(MODDABLE)/examples/io/tcp/fetch/manifest_fetch.json

Then, import the module in your JavaScript source code:

import { fetch } from "fetch";

To use the stream-enabled version of fetch(), include its manifest in your project's manifest.json:

$(MODDABLE)/examples/web/streams/fetch/manifest_fetch.json

Then, import the module in your JavaScript source code:

import { fetch } from "web/fetch/streams";

To use the HTTP Client instead, include its manifest. Including the manifest initializes the host provider device.network.http:

$(MODDABLE)/examples/io/tcp/httpclient/manifest_httpclient.json

For secure requests over HTTPS, include the HTTPS Client manifest instead. It initializes the host provider device.network.https:

$(MODDABLE)/examples/io/tcp/httpsclient/manifest_httpsclient.json

If your project uses the fetch global, mcpack automatically includes the manifest and initializes the fetch global. If your project uses fetch in an import statement, its manifest is automatically included.

To use the stream-enabled version of fetch(), include its manifest as described above under Building with mcconfig

If your project accesses the HTTP Client through device.network.http or device.network.https, mcpack includes the necessary manifests automatically.

• Documentation
  • fetch() on MDN
• Standards
  • fetch() in the WHATWG Fetch Standard
  • HTTP Client in ECMA-419
  • HTTP/1.1 specification RFC
• Examples
  • fetch() example in Moddable SDK
  • HTTP Client example in Moddable SDK
• Implementations
  • fetch() in Moddable SDK
  • HTTP Client in Moddable SDK
• TypeScript Declarations
  • fetch() in Moddable SDK
  • HTTP Client in Moddable SDK