events-middleware
node.js extend EventEmitter to support event middleware
Installation
$ npm install events-middlewareevents-middleware is supported in node v6+.
Usage
import
const {EventEmitter} = require('events-middleware');
const e = new EventEmitter();add listener with middleware
e.middleware('test', function(value1, value2, next) {
next(null, value1, value2);
});select eventNames
// all middleware collection
e.middleware();
// selected middleware collection
e.middleware('test');
e.middleware(['test']);pre or post
const fn = function(value1, value2, next) {
next(null, value1, value2);
};
// if eventName 'test' has added
e.middleware('test').pre(fn).post(fn);
// or not
e.middleware('test1', fn).pre(fn).post(fn);
// use promise
const promiseFn = function(value) {
return Primise.resolve([value]); // return a value list
};
e.middleware('test2', promiseFn).pre(promiseFn).post(promiseFn);
// multiple pre fns or post fns
e.middleware('test').pre(fn).pre(fn);
e.middleware('test').pre([fn, fn]);
// multiple eventNames
e.middleware().pre(fn);
e.middleware(['test', 'test1']).pre(fn);catch error
// middleware fn
const fn = function(value1, value2, next) {
next('return error');
};
// or promise
const promiseFn = function(value1, value2) {
return Promise.reject('return error');
};
const onerror = function(err) {
console.log(err);
};
e.middleware().onError(onerror);
e.middleware('test').onError(onerror);
e.middleware(['test', 'test1']).onError(onerror);emit
e.emit('test', 0, 1);
e.emit('test');remove
e.middleware().remove('test');
e.middleware().remove(['test', 'test1']);clear
e.middleware().clear(); // clear all
// being equivalent to e.middleware().remove(['test', 'test1'])
e.middleware(['test', 'test1']).clear();options
-
globalArgs: (default: false) set to true to let every middleware function accept the values which emit method passed -
multiArgs: (default: true) enable or disable middleware function to pass multiple values to next middleware function -
postMiddleware: (default: true) enable or disable post middlewares -
onlyPromise: (default: false) enable or disable next callback in middleware function
const options = {
globalArgs: false,
multiArgs: true
}
const e1 = new EventEmitter({
middleware: options
});
// or
e1.setOptions({
middleware: options
});
// or by middleware collection
e1.middleware().setOptions(options);
// or when new middleware
e1.middleware('test', fn, options);option globalArgs is true
e1.middleware('test1', function(g, next) {
console.log(g.value); // => 1;
g.value += 1;
next();
}, {
globalArgs: true
}).pre(function(g, next) {
console.log(g.value); // => 0;
g.value += 1;
next();
}).post(function(g, next) {
console.log(g.value); // => 2;
next();
});
e1.emit('test1', {value: 0});option multiArgs is false
e1.middleware('test2', function(value, next) {
// just get first value from pre fn
next(null, value);
}, {
multiArgs: false
}).pre(function(value, next) {
next(null, value, 1); // return two values but pass first value to next
});
e1.emit('test2', 0);option postMiddleware is false
e1.middleware('test3', function(next) {
next();
}, {
postMiddleware: false
}).pre(function(next) {
next();
}).post(function() {
// not to be called
});
e1.emit('test3');option onlyPromise is true
e1.middleware('test4', function(next) {
// next is undefined
}, {
onlyPromise: true
}).pre(function(next) {
// next is undefined
return Promise.resolve();
});
e1.emit('test4');License
MIT
