Node.js 可读流数据事件
原文:https://www . geesforgeks . org/node-js-readable-stream-data-event/
可读流中的“数据”事件在可读时发出。调用 pipe()和 readable.resume()方法将流切换到流动模式，或者向数据事件添加侦听器回调。也可以通过调用 readable.read()方法并返回可用的数据块来引发此事件。
语法:
Event: 'data'
下面的例子说明了数据事件在 Node.js 中的使用:
例 1:
// Node.js program to demonstrate the
// readable data event
// Including fs module
const fs = require('fs');
// Constructing readable stream
const readable = fs.createReadStream("input.txt");
// Instructions to read data
readable.on('readable', () => {
let chunk;
// Using while loop and calling
// read method
while (null !== (chunk = readable.read())) {
// Displaying the chunk
console.log(`read: ${chunk}`);
}
});
// Handling the data event
readable.on('data', (chunk) => {
console.log(`chunk length is: ${chunk.length}`);
});
console.log("Done...");
输出:
Done...
chunk length is: 13
read: GeeksforGeeks
例 2:
// Node.js program to demonstrate the
// readable data event
// Including fs module
const fs = require('fs');
// Constructing readable stream
const readable = fs.createReadStream("input.txt");
// Calling pause method
readable.pause();
// Handling the data event
readable.on('data', (chunk) => {
console.log(`chunk length is: ${chunk.length}`);
});
console.log("Done...");
输出:
Done...
参考:https://nodejs.org/api/stream.html#stream_event_data。
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