Thanks for the snippet. I have taken your var result = new Array(length);
to optimize the array.
Why I use a function for the call back with the result is to play on the
make call now get result latter. Really I'm using this function to update
data in my database.
Array.prototype.forLoop = function(worker, callBack) {
var items = this;
var length = items.length;
var results = new Array(length);
var errors = new Array(length);
var index = 0;
function doNext() {
worker.call(items, items[index], function(err, result) {
results[index] = result;
errors[index] = err;
index++;
if(index === length)
callback(errors, results);
else
process.nextTick(doNext);
});
}
process.nextTick(doNext);
};
On Wednesday, April 11, 2012 5:13:52 PM UTC-4, Tim Caswell wrote:
>
> Ok, so you have a large array and want to do some work on it but break up
> the work across several ticks? That's fine. I still don't understand why
> your workers have a callback if they are sync. So assuming sync workers
> you could do something like:
>
> var queue = [1,2,3,4,5];
>
> function processSlowly(items, work, callback) {
> var length = items.length;
> var results = new Array(length);
> var index = 0;
> function doNext() {
> results[index] = work(items[index]);
> index++;
> if (index === length) return callback(results);
> process.nextTick(doNext);
> }
> process.nextTick(doNext);
> }
>
>
> If your workers are async, you don't need nectTick because the callback is
> already called on a new tick.
>
> function processSerialy(items, work, callback) {
> var length = items.length;
> var results = new Array(length);
> var index = 0;
> function doNext() {
> work(items[index], function (result) {
> results[index] = result;
> index++;
> if (index === length) return callback(results);
> doNext();
> });
> }
> process.nextTick(doNext);
> }
>
> Also note that I don't have any error checking or handling here. I don't
> know if the function should bail out on first error, if it should log the
> error and continue or some other behavior.
>
> On Wed, Apr 11, 2012 at 3:33 PM, Tim Price <price.ti...@gmail.com> wrote:
>
>> OK good point.
>>
>> The stack would be the wrong word. What im trying to do is push eash loop
>> around the array to be in a new cycle around node loop.
>>
>> I'm trying to keep node event loop running fast. The "asyncForEach" can
>> take as long as it need, it would be bulk work. I dont want to through
>> 1000+ function into one cycle around nodes event loop. Now 1000+ is
>> an example as 100+ might be a better real work example.
>>
>> With your asyncForEach would be the same as the forEach that is already
>> part of the language.
>>
>> Maybe you can see why i used the nextTick.
>>
>>
>> On Wednesday, April 11, 2012 4:08:10 PM UTC-4, Tim Caswell wrote:
>>>
>>> My point being that you're showing your worker has a callback. If there
>>> is a callback then I assume it's an async function. The callback will
>>> already be called in a new stack. There is no need to use nextTick to
>>> break the stack. If the worker is a sync function then it should return
>>> it's value instead of passing it via callback. Then you can use
>>> Array.prototype.map as-is to get the resultant array.
>>>
>>> Assuming the worker is async, my parallel example was async and
>>> parallel. If you want async and serial that can be done too similair to
>>> your original example.
>>>
>>> Since you said "Your asyncForEach is at the end of the day synchronous
>>> loop just like any other forloop" I'm confused and somewhere one of your
>>> assumptions is wrong.
>>>
>>> On Wed, Apr 11, 2012 at 3:02 PM, Tim Caswell <t...@creationix.com> wrote:
>>>
>>>> If you just want to keep the stack from growing a simple while or for
>>>> loop is much easier.
>>>>
>>>> var items = [1,2,3,4];
>>>>
>>>> function forEach(items, worker) {
>>>> for (var i = 0, l = items.length; i < l; i++) {
>>>> worker(items[i], i, items);
>>>> }
>>>> }
>>>>
>>>> forEach(items, function (value, index, array) {
>>>> });
>>>>
>>>> or just use the built-in Array.prototype.forEach
>>>>
>>>> items.forEach(function (value, index, array) {
>>>> });
>>>>
>>>> I don't understand the goal. My example was assuming that worker was
>>>> non-blocking and called the callback in a new tick. It was parallel and
>>>> async.
>>>>
>>>>
>>>> On Wed, Apr 11, 2012 at 2:49 PM, Tim Price <price.ti...@gmail.com>wrote:
>>>>
>>>>> I Wanted to keep the items in serially, as im trying to break the
>>>>> stack. Your asyncForEach is at the end of the day synchronous loop just
>>>>> like any other forloop.
>>>>>
>>>>> On Wednesday, April 11, 2012 3:33:18 PM UTC-4, Tim Caswell wrote:
>>>>>>
>>>>>> That depends on what you want it to do. This seems to execute each
>>>>>> item serially. You can do them all parallel and abort on the first
>>>>>> error
>>>>>> like this:
>>>>>>
>>>>>> function asyncForEach(array, worker, callback) {
>>>>>> var len = array.length;
>>>>>> var results = new Array(l);
>>>>>> if (!len) return callback(null, results);
>>>>>> var left = len;
>>>>>> for (var i = 0; i < len; i++) {
>>>>>> start(i);
>>>>>> }
>>>>>> function start(i) {
>>>>>> worker(array[i], i, array, function (err, result) {
>>>>>> if (err) return callback(err);
>>>>>> results[i] = result;
>>>>>> if (!--left) callback(null, results);
>>>>>> });
>>>>>> }
>>>>>> }
>>>>>>
>>>>>>
>>>>>> On Wed, Apr 11, 2012 at 2:07 PM, Tim Price <price.ti...@gmail.com>wrote:
>>>>>>
>>>>>>> How would one better write this function?
>>>>>>>
>>>>>>> Array.prototype.forLoop = function(worker, callBack) {
>>>>>>> var self = this;
>>>>>>> var returnData = [];
>>>>>>> var loop = function(i) {
>>>>>>> if(i === self.length) {
>>>>>>> return callBack(returnData);
>>>>>>> }
>>>>>>> process.nextTick(function() {
>>>>>>>
>>>>>>> worker.call(self, self[i], function(d) {
>>>>>>>
>>>>>>> returnData.push(d);
>>>>>>> loop(++i);
>>>>>>> });
>>>>>>> });
>>>>>>> }
>>>>>>> loop(0);
>>>>>>> };
>>>>>>>
>>>>>>>
>>>>>>> and you would use it like so
>>>>>>>
>>>>>>>
>>>>>>> ['sdf', 'sdfsdf'].forLoop(function(**ite**m, done) {
>>>>>>> console.log(item, done)
>>>>>>> done(item)
>>>>>>> }, function(result) {
>>>>>>> console.log(result)
>>>>>>> })
>>>>>>>
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