数组上的 JavaScript .map 并在满足条件时删除项目 [英] JavaScript .map on an array and removing items if condition satisfied

问题描述

我有一个数组 queue ，当对象被修改时，我将对象推送到它.如果用户按下 save，那么我将遍历 queue 并为它们应用适当的 API 调用.

I have an array queue that I push objects to it when they are modified. If the user presses save, then I will loop through the queue and apply the appropriate API call for them.

如果 API 调用成功，我想从 queue 中删除该项目，否则将其保留在里面并通知用户某些项目未成功保存.我目前有这个(在 AngularJS 中)

If the API call goes through successfully, I want to remove the item from the queue, otherwise keep it inside and notify the user that some items were not successfully saved. I currently have this (in AngularJS)

var unsuccessfulItems = [];
var promise = queue.map(function(item) {
    var defer = $q.defer();
    myCallFunction( item
           , function( response ) {} // Success
           , function( response ) {  // Error
               unsuccessfulItems.push(item);
           }
    )
    defer.resolve();
    return defer.promise;
})
// Once all items have been processed
$q.all( promise ).then( function() {
    queue = unsuccessfulItems;
});

有没有更好的方法来做到这一点?

Is there a better way of doing this?

推荐答案

您已经在使用 Promise，您可能想要端到端地使用它.此外，您过早地兑现了承诺.

You're already using promises, you might want to do it end-to-end. Also, you're resolving the promise too early.

假设您不想承诺 myCallFunction 本身的次优情况，您仍然应该承诺它.

Assuming the suboptimal case where you don't want to promisify myCallFunction itself, you should still promisify it.

function myCall(item){
    var d = $q.defer();
    myCallFunction(item,function(r){ d.resolve({val:r,item:item});}
                       ,function(r){ d.reject(r);});
    return d.promise;
}

注意，我们在异步函数完成之后解析延迟，而不是在它之前.

Note, we are resolving the defer after the asynchronous function is done, not before it.

现在，我们需要实现一个Settle"函数，它会在所有 Promise 完成时进行解析.这就像 $q.all ，但会等待所有的 promise 来解决而不是实现.

Now, we need to implement a "Settle" function, that resolves when all promises are done no matter what. This is like $q.all but will wait for all promises to resolve and not fulfill.

function settle(promises){
     var d = $q.defer();
     var counter = 0;
     var results = Array(promises.length);
     promises.forEach(function(p,i){ 
         p.then(function(v){ // add as fulfilled
              results[i] = {state:"fulfilled", promise : p, value: v};
         }).catch(function(r){ // add as rejected
              results[i] = {state:"rejected", promise : p, reason: r};
         }).finally(function(){  // when any promises resolved or failed
             counter++; // notify the counter
             if (counter === promises.length) {
                d.resolve(results); // resolve the deferred.
             }
         });
     });
}

这种结算函数存在于大多数 promise 实现中，但不存在于 $q 中.我们也可以通过拒绝和 $q.all 来实现这一点，但这意味着流量控制的异常，这是一种不好的做法.

This sort of settle function exists in most promise implementations but not in $q. We could have also done this with rejections and $q.all, but that would mean exceptions for flow control which is a bad practice.

现在，我们可以解决:

 settle(queue.map(myCall)).then(function(results){
     var failed = results.filter(function(r){ return r.state === "rejected"; });
     var failedItems = failed.map(function(i){ return i.value.item; });
 });

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