attach-middleware

Attach middleware functionality onto an object

 
var attachMiddleware = require('attach-middleware')
  , x = {}
;
 
attachMiddleware(x, { useName: 'addMiddleware', runName: 'runMiddleware' });
 
x.addMiddleware(function (obj, next) {
    console.log(obj);
    obj.firstMiddleware = true;
    next();
});
 
x.addMiddleware(function (obj, next) {
    console.log(obj);
    obj.secondMiddleware = true;
    next();
});
 
x.runMiddleware({ hello: 'world' });
// { hello: 'world' }
// { hello: 'world', firstMiddleware: true }
 

Installation

$ npm install attach-middleware

Dependencies

• fast-apply

API

attachMiddleware(obj, [options])

Attach a use method and run method onto an object to enable middleware functionality

• obj - An object to attach the methods. The object may be a constructor's prototype or a plain object
• options
  • useName - Specify the name for the use method (default: 'use')
  • runName - Specify the name for the run method (default: 'run')

.use(fn*)

Add a middleware function to the 'stack'

If the function accepts more arguments than sent through run + 1, than it will be treated as error handling middleware and the first argument will be an error.

If the function does not accept extra arguments and an error has occurred, than it will be bypassed

 
var obj = {};
 
attachMiddleware(obj);
 
obj.use(function (arg1, arg2, next) {
 
    next('error');
    
});
 
obj.use(function (err, arg1, arg2, next) {
    
    console.log(err); // 'error'
    
});
 
obj.run('foo', 'bar');
 

returns this

.run(args*, [callback])

Send arguments through the middleware stack

If the last argument is a function, it is treated as a callback. This function should accept an err and all arguments passed to .run (except the callback function)

returns this

next

The next or callback function passed to each middleware must be called to run the next middleware and eventually, the callback. When calling next, the first argument should be an error or null. Any additional arguments will overwrite the arguments for the rest of the middleware:

 
var obj = {};
 
attachMiddleware(obj);
 
obj.use(function (arg1, arg2, next) {
 
    console.log(arg1, arg2); // 'foo', 'bar'
 
    next(null, 'baz');
    
});
 
obj.use(function (err, arg1, arg2, next) {
    
    console.log(err, arg1, arg2); // null, 'baz', 'bar'
    
});
 
obj.run('foo', 'bar');