Package has same functionality as Node.js Events, however, the emit function will always pomisify all functions called for a certain event.
em = new require('promised-events').PromisedEventEmitter
em.on('f', function(){ return 10; })
em.emit('f').then(function(result){
console.log(result)
}, function(err) {
throw err;
})Will print 10.
fs = require('fs')
em.on('readFileSync', function(path) {
return fs.readFileSync(path);
});
em.emit('readFileSync', '/etc/hostname').then(function (fileContent) {
console.log(fileContent)
}, function(err) {
throw err;
})
})Will print the content of "/etc/hostname" file. If fs.fileReadSync will throw an error, it will be felt without being caught by the fail callback assigned to the promise.
fs = require('fs')
Q = require('q')
em.on('readFile', function(path) {
var defered = Q.defer()
fs.readFile(path, function(err, data) {
if (err) {
defered.reject(err)
} else {
defered.resolve(data)
}
})
return defered.promise
});
em.emit('readFile', '/etc/hostname').then(function (fileContent) {
console.log(fileContent)
}, function(err) {
throw err
})Will print the content of "/etc/hostname" file or throw the error sent to the fail callback assigned to the promise.
fs = require('fs')
Q = require('q')
// first callback
em.on('read', function(path) {
return fs.readFileSync(path);
});
// second callback
em.on('read', function(path) {
var defered = Q.defer()
fs.readFile(path, function(err, data) {
if (err) {
defered.reject(err)
} else {
defered.resolve(data)
}
})
return defered.promise
});
// trigger event
em.emit('read', '/etc/hostname').then(function (readConent) {
for (var i = 0; i < readContent.length; i++) {
console.log(readContent[i])
}
}, function(err) {
throw err
})
})If all callbacks will run without errors, readContent will return an array of results, for each promised function. Otherwise, it will throw the first encountered error.