writable.setDefaultEncoding()方法是Stream模块的内置应用程序编程接口,用于为Writable流设置默认编码。
用法:
writable.setDefaultEncoding( encoding )
参数:此方法接受单参数编码,该参数保留要用于可写流的编码。
返回值:它返回默认编码。
以下示例说明了Node.js中writable.setDefaultEncoding()方法的使用:
范例1:
// Node.js program to demonstrate the
// writable.setDefaultEncoding() method
const stream = require('stream');
// Creating a stream and creating
// a write function
const writable = new stream.Writable({
// Write function with its
// parameters
write:function(chunk, encoding, next) {
// Converting the chunk of
// data to string
console.log(chunk.toString());
next();
}
});
// Writing data
writable.write('hi');
// Calling setDefaultEncoding method
writable.setDefaultEncoding("utf8");
输出:
hi Writable { _writableState: WritableState { objectMode:false, highWaterMark:16384, finalCalled:false, needDrain:false, ending:false, ended:false, finished:false, destroyed:false, decodeStrings:true, defaultEncoding:'utf8', length:0, writing:false, corked:0, sync:false, bufferProcessing:false, onwrite:[Function:bound onwrite], writecb:null, writelen:0, bufferedRequest:null, lastBufferedRequest:null, pendingcb:1, prefinished:false, errorEmitted:false, emitClose:true, autoDestroy:false, bufferedRequestCount:0, corkedRequestsFree: { next:null, entry:null, finish:[Function:bound onCorkedFinish] } }, writable:true, _write:[Function:write], domain:null, _events:[Object:null prototype] {}, _eventsCount:0, _maxListeners:undefined }
此处,默认值在输出中返回。
范例2:
// Node.js program to demonstrate the
// writable.setDefaultEncoding() method
const stream = require('stream');
// Creating a stream and creating
// a write function
const writable = new stream.Writable({
// Write function with its
// parameters
write:function(chunk, encoding, next) {
// Converting the chunk of
// data to string
console.log(chunk.toString());
next();
}
});
// Writing data
writable.write('hi');
// Calling setDefaultEncoding method
writable.setDefaultEncoding("ascii");
输出:
hi Writable { _writableState: WritableState { objectMode:false, highWaterMark:16384, finalCalled:false, needDrain:false, ending:false, ended:false, finished:false, destroyed:false, decodeStrings:true, defaultEncoding:'ascii', length:0, writing:false, corked:0, sync:false, bufferProcessing:false, onwrite:[Function:bound onwrite], writecb:null, writelen:0, bufferedRequest:null, lastBufferedRequest:null, pendingcb:1, prefinished:false, errorEmitted:false, emitClose:true, autoDestroy:false, bufferedRequestCount:0, corkedRequestsFree: { next:null, entry:null, finish:[Function:bound onCorkedFinish] } }, writable:true, _write:[Function:write], domain:null, _events:[Object:null prototype] {}, _eventsCount:0, _maxListeners:undefined }
此处,默认值为“ascii”。
参考: https://nodejs.org/api/stream.html#stream_writable_setdefaultencoding_encoding
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