node.js cujojs/when sequenceのサンプル。非同期処理の古典

when_sequence_example.js

// npm install --save when

var when = require('when');
var sequence = require('when/sequence');

var ready = sequence([
    function() { return prm1(); },
    function() { return prm2(); },
    function() { return prm3(); }
]);

when(ready).then(function(data) {
    console.info(data); // [ 'OK1', 'OK2', 'OK3' ] prm1,2,3のreqolveが配列で渡される
    console.log('sequence completed!');
    var prm = when.defer();
    setTimeout(function() {
        prm.resolve(data[1]);
    }, 500);
    return prm.promise;
}).then(function(data) {
    console.log('prm2 data is ' + data);
});


var prm1 = function() {
    console.log("exec prm1...");
    var prm = when.defer();
    setTimeout(function() {
        prm.resolve('OK1');
    }, 500);
    //prm.reject('Error1');
    return prm.promise;
    //return 'p1';
};

var prm2 = function(data) {
    console.log("exec prm2...");
    console.log(data);  // undefined prm1のresolveは渡されない
    var prm = when.defer();
    setTimeout(function() {
        prm.resolve('OK2');
    }, 500);
    return prm.promise;
};

var prm3 = function() {
    console.log("exec prm3...");
    var prm = when.defer();
    setTimeout(function() {
        prm.resolve('OK3');
    }, 500);
    return prm.promise;
};