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WritableStreamDefaultWriter()
构造函数创建新
WritableStreamDefaultWriter
对象实例。
注意
: You generally wouldn't use this constructor manually; instead, you'd use the
WritableStream.getWriter()
方法。
var writableStreamDefaultWriter = new WritableStreamDefaultWriter(stream);
WritableStream
to be written to.
An instance of the
WritableStreamDefaultWriter
对象。
stream
value is not a
WritableStream
, or it is locked to another writer already.
The following example shows the creation of a
WritableStream
with a custom sink and an API-supplied queuing strategy. It then calls a function called
sendMessage()
, passing the newly created stream and a string. Inside this function it calls the stream's
getWriter()
method, which returns an instance of
WritableStreamDefaultWriter
。
forEach()
call is used to write each chunk of the string to the stream. Finally,
write()
and
close()
return promises that are processed to deal with success or failure of chunks and streams.
const list = document.querySelector('ul');
function sendMessage(message, writableStream) {
// defaultWriter is of type WritableStreamDefaultWriter
const defaultWriter = writableStream.getWriter();
const encoder = new TextEncoder();
const encoded = encoder.encode(message, { stream: true });
encoded.forEach((chunk) => {
defaultWriter.ready
.then(() => {
return defaultWriter.write(chunk);
})
.then(() => {
console.log("Chunk written to sink.");
})
.catch((err) => {
console.log("Chunk error:", err);
});
});
// Call ready again to ensure that all chunks are written
// before closing the writer.
defaultWriter.ready
.then(() => {
defaultWriter.close();
})
.then(() => {
console.log("All chunks written");
})
.catch((err) => {
console.log("Stream error:", err);
});
}
const decoder = new TextDecoder("utf-8");
const queuingStrategy = new CountQueuingStrategy({ highWaterMark: 1 });
let result = "";
const writableStream = new WritableStream({
// Implement the sink
write(chunk) {
return new Promise((resolve, reject) => {
var buffer = new ArrayBuffer(2);
var view = new Uint16Array(buffer);
view[0] = chunk;
var decoded = decoder.decode(view, { stream: true });
var listItem = document.createElement('li');
listItem.textContent = "Chunk decoded: " + decoded;
list.appendChild(listItem);
result += decoded;
resolve();
});
},
close() {
var listItem = document.createElement('li');
listItem.textContent = "[MESSAGE RECEIVED] " + result;
list.appendChild(listItem);
},
abort(err) {
console.log("Sink error:", err);
}
}, queuingStrategy);
sendMessage("Hello, world.", writableStream);
You can find the full code in our Simple writer example .
| 规范 | 状态 | 注释 |
|---|---|---|
|
流
The definition of 'WritableStreamDefaultWriter()' in that specification. |
实时标准 | 初始定义。 |
| 桌面 | 移动 | |||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
WritableStreamDefaultWriter()
构造函数
|
Chrome 59 | Edge 16 | Firefox No | IE No | Opera 46 | Safari ? | WebView Android 59 | Chrome Android 59 | Firefox Android No | Opera Android 43 | Safari iOS ? | Samsung Internet Android 7.0 |
完整支持
不支持
兼容性未知
实验。期望将来行为有所改变。
WritableStreamDefaultWriter
WritableStreamDefaultWriter()