基於JavaScript系列的控制流程

Question

在Mixu的Node.js書籍中，有一篇關於控制流程的非常棒的章節。以下模式允許您鏈接異步請求以確保在調用下一個事件之前事件已完成。我想修改它，以便來自一個異步請求的響應可以作爲參數傳遞給下一個。

任何想法？

http://book.mixu.net/node/ch7.html http://jsfiddle.net/B7xGn/

function series(callbacks, last) { 
    var results = []; 
    function next() { 
    var callback = callbacks.shift(); 
    if(callback) { 
     callback(function() { 
     results.push(Array.prototype.slice.call(arguments)); 
     next(); 
     }); 
    } else { 
     last(results); 
    } 
    } 
    next(); 
} 
// Example task 
function async(arg, callback) { 
    var delay = Math.floor(Math.random() * 5 + 1) * 100; // random ms 
    console.log('async with \''+arg+'\', return in '+delay+' ms'); 
    setTimeout(function() { callback(arg * 2); }, delay); 
} 
function final(results) { console.log('Done', results); } 

series([ 
    function(next) { async(1, next); }, 
    function(next) { async(2, next); }, 
    function(next) { async(3, next); }, 
    function(next) { async(4, next); }, 
    function(next) { async(5, next); }, 
    function(next) { async(6, next); } 
], final); 

Answer 1

您可以更改next函數簽名，這樣就可以通過它result。以下是你如何做到這一點。

function series(callbacks, last) { 
    var results = []; 
    function next(result) { 
    var callback = callbacks.shift(); 
    if(callback) { 
     callback(function(result) { 
     results.push(Array.prototype.slice.call(arguments)); 
     next(result); 
     }, result); 
    } else { 
     last(results); 
    } 
    } 
    next(); 
} 
// Example task 
function async(arg, callback) { 
    var delay = Math.floor(Math.random() * 5 + 1) * 100; // random ms 
    console.log('async with \''+arg+'\', return in '+delay+' ms'); 
    setTimeout(function() { callback(arg * 2); }, delay); 
} 

function final(results) { console.log('Done', results); } 

series([ 
    function(next) { async(1, next); }, 
    function(next, result) { console.log('result: ', result); async(2, next); }, 
    function(next, result) { console.log('result: ', result); async(3, next); }, 
    function(next, result) { console.log('result: ', result); async(4, next); }, 
    function(next, result) { console.log('result: ', result); async(5, next); }, 
    function(next, result) { console.log('result: ', result); async(6, next); } 
], final); 

編輯：

爲了能夠通過多個結果，你可以簡單地改變一系列功能：

function series(callbacks, last) { 
    var results = []; 
    function next() { 
    var callback = callbacks.shift(), args; 
    if(callback) { 
     callback.apply(this, (args = [ 
     function() { 
      results.push(Array.prototype.slice.call(arguments)); 
      next.apply(this, arguments); 
     } 
     ]).concat.apply(args, arguments)); 
    } else { 
     last(results); 
    } 
    } 
    next(); 
}