多次运行$ .ajax() [英] Running $.ajax() Multiple Times

问题描述

我有一个jQuery $ .ajax()函数，成功返回一个base64值(即pdf页).我必须返回多个base64值，因此我想到的唯一方法是遍历$ .ajax()函数.当返回每个成功时，我将base64值写入一个image元素.这很好.问题是，因为它是异步的，所以不一定按顺序返回页面. 我知道这不是最好的方法，但是如果我总是要有一个不同的值(页数)，该如何链接它?

I have a jQuery $.ajax() function that is returning a base64 value's, which are pdf pages, on success. I have to return multiple base64 values, so the only way that I could think of how to do this, is to loop through the $.ajax() function. When each success is returned, I write the base64 value into an image element. This works fine. The problem is, because it is asynchronous, it does not necessarily return the pages in order. I understand that it isn't the best method, but how can I chain this if I am always going to have a different value, which is the page count?

    for (i = 1; i <= pdfPageCount; i++) {
            $.ajax({
                type: 'POST',
                contentType: 'application/json',
                url: 'Page.aspx/Method',
                 dataType: 'json',
                error: function (err) {
                    alert('Error: ' + err);
                },

                 success: function (resultStr) {
                    //alert('Page: ' + i);

                    var sigImage = document.createElement("img");
                    sigImage.setAttribute('src', 'data:image/png;base64,' + 
    resultStr.d);

                    document.getElementById("imgId").appendChild(sigImage);
                },
            });
    } // end the for loop

HTML只是有一个div:

The HTML just has a div:

    <form id="form1" runat="server">
    <div id="imgId">
    </div>
    </form>

推荐答案

它们的关键是使用何时.虽然您可以以同步方式链接呼叫，但我不建议这样做.更好的方法是异步调用每个页面，然后同时等待所有结果.

They key is to use when. While you can chain your calls in a synchronous manner, I wouldn't suggest it. A better approach would be to asynchronously call for each page, then await all the results simultaneously.

var pages = [];
var deferredObjs = [];
for (i = 0; i <= pdfPageCount; i++) {
            deferredObjs[i] = $.ajax({
                type: 'POST',
                contentType: 'application/json',
                url: 'Page.aspx/Method',
                dataType: 'json',
                error: function (err) {
                alert('Error: ' + err);
            },

             success: function (resultStr) {
             pages[i] = resultStr;
            },
        });
} // end the for loop


$.when.apply( $, deferredObjs ).then( aFunctionToProcessPageResults() );

此外，您的POST不应提供要返回的页码吗?请注意，我将索引变量更改为以0开头.您可能需要对此进行说明.

Also, shouldn't your POST be supplying the page number to return? Note that I changed your index variable to start a 0. You may need to account for this.

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