Nodejs 异步代码模式实战

1.输出当前目录下的所有文件的文件名

#Synchronous #

var fs = require('fs'),
    filenames,
    i,
    processId;

filenames = fs.readdirSync(".");
for (i = 0; i < filenames.length; i++) {
    console.log(filenames[i]);
}

console.log("Ready.");
processId = process.getuid();

#Asynchronous#

var fs = require('fs'),
      processId;

fs.readdir(".", function (err, filenames) {
    var i;
    for (i = 0; i < filenames.length; i++) {
        console.log(filenames[i]);
    }
    console.log("Ready.");
});

processId = process.getuid();

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2.授权，重命名

#Synchronous #

var fs = require('fs'),
    oldFilename,
    newFilename,
    isSymLink;

oldFilename = "./processId.txt";
newFilename = "./processIdOld.txt";

fs.chmodSync(oldFilename, 777);
fs.renameSync(oldFilename, newFilename);

isSymLink = fs.lstatSync(newFilename).isSymbolicLink();

#Asynchronous#

var fs = require('fs'),
    oldFilename,
    newFilename;


oldFilename = "./processId.txt";
newFilename = "./processIdOld.txt";

fs.chmod(oldFilename, 777, function (err) {   
    fs.rename(oldFilename, newFilename, function (err) {
        fs.lstat(newFilename, function (err, stats) {
            var isSymLink = stats.isSymbolicLink();
        });
    });
});

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3.获得当前目录下所有文件的大小

#Synchronous #

var fs = require('fs');

function calculateByteSize() {
    var totalBytes = 0,
        i,
        filenames,
        stats;
    filenames = fs.readdirSync(".");
    for (i = 0; i < filenames.length; i ++) {
        stats = fs.statSync("./" + filenames[i]);
        totalBytes += stats.size;
    }
    console.log(totalBytes);
}

calculateByteSize();

#Asynchronous#

var fs = require('fs');

var count = 0,
    totalBytes = 0;

function calculateByteSize() {
    fs.readdir(".", function (err, filenames) {
        var i;
        count = filenames.length;


        for (i = 0; i < filenames.length; i++) {
            fs.stat("./" + filenames[i], function (err, stats) {
                totalBytes += stats.size;
                count--;
                if (count === 0) {
                    console.log(totalBytes);
                }
            });
        }
    });
}

#Asynchronous#


calculateByteSize();

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4.计算文件数

#Synchronous #

var fs = require('fs');

var path1 = "./",
    path2 = ".././";

function countFiles(path) {
    var filenames = fs.readdirSync(path);
    return filenames.length;
}

console.log(countFiles(path1) + " files in " + path1);
console.log(countFiles(path2) + " files in " + path2);

#Asynchronous#

var fs = require('fs');

var path1 = "./",
    path2 = ".././",
    logCount;

function countFiles(path, callback) {
    fs.readdir(path, function (err, filenames) {
        callback(err, path, filenames.length);
    });
}

logCount = function (err, path, count) {
    console.log(count + " files in " + path);
};

countFiles(path1, logCount); 
countFiles(path2, logCount);