如何在没有承诺的情况下处理异步函数? [英] How to deal with asynchronous functions without promises?

问题描述

我开始使用angularJS进行web应用程序开发，该程序带有一个promise库，但是现在我必须在没有项目的情况下进行另一个项目的开发.我将如何执行此操作而无需导入Promise库.

I started doing web-app development with angularJS which comes with a promise library but now I have to work on another project without one. How would I do this without having to import a promise library.

我已经删除了一些不相关的内容，但是基本上我需要从后端获取文件url，基于该url创建一个元素，然后返回该元素.事情是一旦进入异步函数，我就不知道如何返回以返回创建的元素.

I've removed some of the irrelevant things but basically I need to get a file url from the backend, create an element based on this url, and then return the element. The thing is once I go inside the async function, I don't know how to get back out to return the created element.

        var userLogoAWS = null;
        $.get("http://localhost:8080/apps/admin/file",
               {
                category: category,
                filename: "logo.png"
               },
               function(data){
                userLogoAWS = data;
               });

        img.src   = userLogoAWS;

        //---- Create and Combine elements ----
        var element = anchor.appendChild(img);

        return element;

推荐答案

在这种情况下，我将利用简单的回调模式.有很多方法可以做到这一点，但关键是要传递一个处理ajax调用成功的函数作为进行ajax调用的函数的参数.

I would take advantage of a simple callback pattern in this case. there are a lot of ways to do this but the key thing is passing a function that handles the success of the ajax call as an argument to the function that makes the ajax call.

function getLogo(createElement){
   $.get("http://localhost:8080/apps/admin/file",
               {
                category: category,
                filename: "logo.png"
               },
               function(data){
                 createElement(data)
               });
}

function createElement(logo){
   var img = new Image();
   img.src = logo;
   var element = anchor.appendChild(img);
   return element; //or assign element to a global variable
}

var element = getLogo(createElement);

如果这不起作用，则JQuery具有一个Promise库，看来您正在使用jquery，所以为什么不利用它.

if this does not work, JQuery has a promise library and it seems you are using jquery, so why not take advantage of that.

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