javascript:用一个回调执行一堆异步方法 [英] javascript: execute a bunch of asynchronous method with one callback

问题描述

我需要执行一堆异步方法(客户端 SQLite 数据库)，并且只调用一个最终回调.

I need to execute a bunch of asynchronous methods (client SQLite database), and call only one final callback.

当然，丑陋的方式是:

execAll : function(callBack) {
        asynch1(function() {
            asynch2(function() {
                ...
                asynchN(function() {
                    callBack();
                })
            })
        });
    }

但我知道有更好的方法来做到这一点.直觉上，我会检测何时所有回调都被调用，并使用计数器调用最终回调.

But I know there are better ways to do it. Intuitively I would detect when all call back has been called with a counter to call the final callback.

我认为这是一个常见的设计模式，所以如果有人能指出我正确的方向......

I think this is a common design-pattern, so if someone could point me in the right direction...

提前致谢！

推荐答案

这很容易

var callback = (function(){
    var finishedCalls = 0;
    return function(){
        if (++finishedCalls == 4){
             //execute your action here
        }
    };
})();

只需将此回调传递给您的所有方法，一旦它被调用 4 次，它就会执行.

Just pass this callback to all your methods, and once it has been called 4 times it will execute.

如果您想为此使用工厂，则可以执行以下操作

If you want to use factory for this then you can do the following

function createCallback(limit, fn){
    var finishedCalls = 0;
    return function(){
        if (++finishedCalls == limit){
             fn();
        }
    };
}


var callback = createCallback(4, function(){
    alert("woot!");
});


async1(callback);
async2(callback);
async3(callback);
async4(callback);

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