node.js - NodeJS：用generic flow control来解决boomerang效应的疑惑
这段代码是在node高级编程19章Listing 19-3，cascade function 看不明白，能帮忙给解释下吗？
var fs = require('fs');
function cascade(callbacks, callback) {
// clone the array
var functions = callbacks.slice(0);
function processNext(err) {
if (err) {
return callback(err);
}
var args = Array.prototype.slice.call(arguments);
var func = functions.shift();
if (func) {
// remove first argument containing the error
args.shift();
} else {
func = callback;
}
args.push(processNext);
func.apply(this, args);
}
processNext.call(this);
}
function append_some_a_to_b(callback) {
var aFd, bFd,
buffer = new Buffer(10);
cascade([
function open_a(next) {
fs.open(__dirname + '/a.txt', 'r', next);
},
function read_from_a(fd, next) {
aFd = fd;
fs.read(aFd, buffer, 0, buffer.length, 0, next);
},
function close_a(bytesRead, buf, next) {
fs.close(aFd, next);
},
function open_b(next) {
fs.open(__dirname + '/b.txt', 'a', next);
},
function stat_b(fd, next) {
bFd = fd;
fs.fstat(bFd, next);
},
function write_b(bStats, next) {
fs.write(bFd, buffer, 0, buffer.length, bStats.size, next);
},
function close_b(bytesWritten, buf, next) {
fs.close(bFd, next);
}
], callback);
};
console.log('starting...');
append_some_a_to_b(function done(err) {
if (err) {
throw err;
}
console.log('done');
});
谢谢各位了！
