mirror of https://github.com/jkjoy/sunpeiwen.git
145 lines
7.1 KiB
Markdown
145 lines
7.1 KiB
Markdown
# stream-http [](https://travis-ci.org/jhiesey/stream-http)
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[](https://saucelabs.com/u/stream-http)
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This module is an implementation of Node's native `http` module for the browser.
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It tries to match Node's API and behavior as closely as possible, but some features
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aren't available, since browsers don't give nearly as much control over requests.
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This is heavily inspired by, and intended to replace, [http-browserify](https://github.com/substack/http-browserify).
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## What does it do?
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In accordance with its name, `stream-http` tries to provide data to its caller before
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the request has completed whenever possible.
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Backpressure, allowing the browser to only pull data from the server as fast as it is
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consumed, is supported in:
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* Chrome >= 58 (using `fetch` and `WritableStream`)
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The following browsers support true streaming, where only a small amount of the request
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has to be held in memory at once:
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* Chrome >= 43 (using the `fetch` API)
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* Firefox >= 9 (using `moz-chunked-arraybuffer` responseType with xhr)
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The following browsers support pseudo-streaming, where the data is available before the
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request finishes, but the entire response must be held in memory:
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* Chrome
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* Safari >= 5, and maybe older
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* IE >= 10
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* Most other Webkit-based browsers, including the default Android browser
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All browsers newer than IE8 support binary responses. All of the above browsers that
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support true streaming or pseudo-streaming support that for binary data as well
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except for IE10. Old (presto-based) Opera also does not support binary streaming either.
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### IE8 note:
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As of version 2.0.0, IE8 support requires the user to supply polyfills for
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`Object.keys`, `Array.prototype.forEach`, and `Array.prototype.indexOf`. Example
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implementations are provided in [ie8-polyfill.js](ie8-polyfill.js); alternately,
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you may want to consider using [es5-shim](https://github.com/es-shims/es5-shim).
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All browsers with full ES5 support shouldn't require any polyfills.
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## How do you use it?
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The intent is to have the same API as the client part of the
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[Node HTTP module](https://nodejs.org/api/http.html). The interfaces are the same wherever
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practical, although limitations in browsers make an exact clone of the Node API impossible.
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This module implements `http.request`, `http.get`, and most of `http.ClientRequest`
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and `http.IncomingMessage` in addition to `http.METHODS` and `http.STATUS_CODES`. See the
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Node docs for how these work.
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### Extra features compared to Node
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* The `message.url` property provides access to the final URL after all redirects. This
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is useful since the browser follows all redirects silently, unlike Node. It is available
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in Chrome 37 and newer, Firefox 32 and newer, and Safari 9 and newer.
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* The `options.withCredentials` boolean flag, used to indicate if the browser should send
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cookies or authentication information with a CORS request. Default false.
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This module has to make some tradeoffs to support binary data and/or streaming. Generally,
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the module can make a fairly good decision about which underlying browser features to use,
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but sometimes it helps to get a little input from the developer.
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* The `options.mode` field passed into `http.request` or `http.get` can take on one of the
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following values:
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* 'default' (or any falsy value, including `undefined`): Try to provide partial data before
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the request completes, but not at the cost of correctness for binary data or correctness of
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the 'content-type' response header. This mode will also avoid slower code paths whenever
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possible, which is particularly useful when making large requests in a browser like Safari
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that has a weaker JavaScript engine.
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* 'allow-wrong-content-type': Provides partial data in more cases than 'default', but
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at the expense of causing the 'content-type' response header to be incorrectly reported
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(as 'text/plain; charset=x-user-defined') in some browsers, notably Safari and Chrome 42
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and older. Preserves binary data whenever possible. In some cases the implementation may
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also be a bit slow. This was the default in versions of this module before 1.5.
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* 'prefer-stream': Provide data before the request completes even if binary data (anything
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that isn't a single-byte ASCII or UTF8 character) will be corrupted. Of course, this option
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is only safe for text data. May also cause the 'content-type' response header to be
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incorrectly reported (as 'text/plain; charset=x-user-defined').
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* 'disable-fetch': Force the use of plain XHR regardless of the browser declaring a fetch
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capability. Preserves the correctness of binary data and the 'content-type' response header.
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* 'prefer-fast': Deprecated; now a synonym for 'default', which has the same performance
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characteristics as this mode did in versions before 1.5.
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* `options.requestTimeout` allows setting a timeout in millisecionds for XHR and fetch (if
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supported by the browser). This is a limit on how long the entire process takes from
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beginning to end. Note that this is not the same as the node `setTimeout` functions,
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which apply to pauses in data transfer over the underlying socket, or the node `timeout`
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option, which applies to opening the connection.
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### Features missing compared to Node
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* `http.Agent` is only a stub
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* The 'socket', 'connect', 'upgrade', and 'continue' events on `http.ClientRequest`.
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* Any operations, including `request.setTimeout`, that operate directly on the underlying
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socket.
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* Any options that are disallowed for security reasons. This includes setting or getting
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certain headers.
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* `message.httpVersion`
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* `message.rawHeaders` is modified by the browser, and may not quite match what is sent by
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the server.
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* `message.trailers` and `message.rawTrailers` will remain empty.
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* Redirects are followed silently by the browser, so it isn't possible to access the 301/302
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redirect pages.
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* The `timeout` event/option and `setTimeout` functions, which operate on the underlying
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socket, are not available. However, see `options.requestTimeout` above.
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## Example
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``` js
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http.get('/bundle.js', function (res) {
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var div = document.getElementById('result');
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div.innerHTML += 'GET /beep<br>';
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res.on('data', function (buf) {
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div.innerHTML += buf;
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});
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res.on('end', function () {
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div.innerHTML += '<br>__END__';
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});
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})
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```
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## Running tests
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There are two sets of tests: the tests that run in Node (found in `test/node`) and the tests
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that run in the browser (found in `test/browser`). Normally the browser tests run on
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[Sauce Labs](http://saucelabs.com/).
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Running `npm test` will run both sets of tests, but in order for the Sauce Labs tests to run
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you will need to sign up for an account (free for open source projects) and put the
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credentials in a [`.zuulrc` file](https://github.com/defunctzombie/zuul/wiki/zuulrc).
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To run just the Node tests, run `npm run test-node`.
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To run the browser tests locally, run `npm run test-browser-local` and point your browser to
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`http://localhost:8080/__zuul`
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## License
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MIT. Copyright (C) John Hiesey and other contributors.
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