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Allows easy composition of a chain of connect.js-style middlewares
// Allows easy composition of a chain of connect.js-style middlewares in node.js
// given:
// function A(req,res,next){}
// function B(req,res,next){}
// composeMiddleware(A,B) will return a function(req,res,next) that passes the request
// through both handlers, just like Connect. If a next() is called with an error
// the call chain is stopped and the error is passed to the topmost next()
// If next() is called with the second parameter set to 'break' "next(null, 'break')"
// The chain is halted and route control is passed back to the original next()
function composeMiddleware(){
var layers = Array.prototype.slice.call(arguments);
var handler = function(req,res,next){
var i = 0;
// This is passed as the next() parameter
function nextLayer(err, escapeStack){
if(err) return next(err);
// if the second param is 'break', break out of this stack by calling
// the original next()
if(escapeStack == 'break') return next();
// if there are still layers left
if(i < layers.length){
var layer = layers[i++];
layer(req, res, nextLayer);
} else next(); // we're done with the stack.
}
nextLayer();
}
return handler;
}
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