js001 ---- async

async.waterfall([
    function(callback) {
        callback(null, \'one\', \'two\');
    },
    function(arg1, arg2, callback) {
        // arg1 now equals \'one\' and arg2 now equals \'two\'
        callback(null, \'three\');
    },
    function(arg1, callback) {
        // arg1 now equals \'three\'
        callback(null, \'done\');
    }
], function (err, result) {
    // result now equals \'done\'
});

// Or, with named functions:
async.waterfall([
    myFirstFunction,
    mySecondFunction,
    myLastFunction,
], function (err, result) {
    // result now equals \'done\'
});
function myFirstFunction(callback) {
    callback(null, \'one\', \'two\');
}
function mySecondFunction(arg1, arg2, callback) {
    // arg1 now equals \'one\' and arg2 now equals \'two\'
    callback(null, \'three\');
}
function myLastFunction(arg1, callback) {
    // arg1 now equals \'three\'
    callback(null, \'done\');
}

async.parallel([
    function(callback) {
        setTimeout(function() {
            callback(null, \'one\');
        }, 200);
    },
    function(callback) {
        setTimeout(function() {
            callback(null, \'two\');
        }, 100);
    }
],
// optional callback
function(err, results) {
    // the results array will equal [\'one\',\'two\'] even though
    // the second function had a shorter timeout.
});

// an example using an   instead of an array
async.parallel({
    one: function(callback) {
        setTimeout(function() {
            callback(null, 1);
        }, 200);
    },
    two: function(callback) {
        setTimeout(function() {
            callback(null, 2);
        }, 100);
    }
}, function(err, results) {
    // results is now equals to: {one: 1, two: 2}
});

// assuming openFiles is an array of file names and saveFile is a function
// to save the modified contents of that file:

async.each(openFiles, saveFile, function(err){
  // if any of the saves produced an error, err would equal that error
});

// assuming openFiles is an array of file names
async.each(openFiles, function(file, callback) {

    // Perform operation on file here.
    console.log(\'Processing file \' + file);

    if( file.length > 32 ) {
      console.log(\'This file name is too long\');
      callback(\'File name too long\');
    } else {
      // Do work to process file here
      console.log(\'File processed\');
      callback();
    }
}, function(err) {
    // if any of the file processing produced an error, err would equal that error
    if( err ) {
      // One of the iterations produced an error.
      // All processing will now stop.
      console.log(\'A file failed to process\');
    } else {
      console.log(\'All files have been processed successfully\');
    }
});