集合(二) each - sanlex/async_chinese GitHub Wiki

// 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');
    }
});

var obj = {dev: "/dev.json", test: "/test.json", prod: "/prod.json"};
var configs = {};

async.forEachOf(obj, function (value, key, callback) {
    fs.readFile(__dirname + value, "utf8", function (err, data) {
        if (err) return callback(err);
        try {
            configs[key] = JSON.parse(data);
        } catch (e) {
            return callback(e);
        }
        callback();
    });
}, function (err) {
    if (err) console.error(err.message);
    // configs is now a map of JSON data
    doSomethingWith(configs);
});