譯 理解 NodeJS 中基於事件驅動的架構

本文講的是[譯] 理解 nodejs 中基於事件驅動的架構，

譯文出自：掘金翻譯計畫

譯者：劉德元

薛丁格的貓

校對者：bambooom

zaraguo

function

filesize (filename, cb) 
fs.stat(filename, (err, stats) =>  // 非同步
cb(null, stats.size); // 非同步
});}

const readfileasarray = function(file, cb) 

const lines = data.tostring().trim().split('\n');
cb(null, lines);
});};

10

1112
1314
15

readfileasarray('./numbers.txt', (err, lines) => );

readfileasarray('./numbers.txt')

.then(lines => )
.catch(console.error);

const readfileasarray = function(file, cb = () => {}) 

const lines = data.tostring().trim().split('\n');
resolve(lines);
cb(null, lines);
});});
};

async

function
countodd ()  catch(err) 
}countodd();

class

myemitter
extends
eventemitter

const myemitter = new myemitter();

const eventemitter = require('events');

class
withlog
extends
eventemitter
}const withlog = new withlog();
withlog.on('begin', () => console.log('about to execute'));
withlog.on('end', () => console.log('done with execute'));
withlog.execute(() =>
console.log('*** executing task ***'));

before executing

about to execute
*** executing task ***
done with execute
after executing

內含方法的執行輸出了「*** executing task ***」；

另乙個命名事件輸出「done with execute」；

最後「after executing」。

// ...

withlog.execute(() => );
});

before executing

about to execute
done with execute
after executing
*** executing task ***

const fs = require('fs');

const eventemitter = require('events');
class
withtime
extends
eventemitter
this.emit('data', data);
console.timeend('execute');
this.emit('end');
});}}
const withtime = new withtime();
withtime.on('begin', () => console.log('about to execute'));
withtime.on('end', () => console.log('done with execute'));
withtime.execute(fs.readfile, __filename);

about to execute

execute: 4.507ms
done with execute

class

withtime
extends
eventemitter
catch(err) 
}}

this.emit('error', err);

this.emit('data', data);

withtime.on('data', (data) => );

class

withtime
extends
eventemitter
console.timeend('execute');
});}}
const withtime = new withtime();
withtime.execute(fs.readfile, ''); // bad call
withtime.execute(fs.readfile, __filename);

events.js:163

throw er; // unhandled 'error' event
^error: enoent: no such file or directory, open ''

withtime.on('error', (err) => );

execute: 4.276ms

unhandledpromiserejectionwarning: unhandled promise rejection (rejection id: 1): error: enoent: no such file or directory, open ''

deprecationwarning: unhandled promise rejections are deprecated. in the future, promise rejections that are not handled will terminate the node.js process with a non-zero exit code.

process.on('uncaughtexception', (err) => );

withtime.on('data', (data) => `);

});withtime.on('data', (data) => `);
});withtime.execute(fs.readfile, __filename);

withtime.on('data', (data) => `);

});withtime.prependlistener('data', (data) => `);
});withtime.execute(fs.readfile, __filename);

原文發布時間為：2023年6月07日

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