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POFirefox Extension: multiple requests with XMLHttpRequest. Use Asynchronous or not?
 

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  1. POFirefox Extension: multiple requests with XMLHttpRequest. Use Asynchronous or not?
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    <p>I'm trying something very simple for my first Firefox Add-On, the important part is:</p> <p>Step 1) Call an external API to retrieve some data.<br> Step 2) Call that API again with the data retrieved the first time to get some more.</p> <p>Now, I first implemented it using XMLHttpRequest in synchronous mode, since I thought the need to wait for Step 2 forced me to do it that way. Two calls to the function that dealt with the API call, used XMLHttpRequest and parsed the response. Fine.</p> <p>Then I came accross various docs in the Mozilla Development Network which encourage you to use XMLHttpRequest in asynchronous mode and so I tried.</p> <p>Basing my implementation on <a href="https://stackoverflow.com/questions/1203074/firefox-extension-multiple-xmlhttprequest-calls-per-page">multiple XMLHttpRequests</a> and others I came up with the code below.</p> <p>My question is: Is this the proper way to do it? Should I go back to using synchronous mode? It works like this, but it just doesn't strike me as the correct AJAX pattern you would use...</p> <pre><code> // first call var username = foo; var password = bar; var startOffset = 0; // initial value var url = encodeURIComponent('https://theapiurl.com/query=' + startOffset); doRequest(); function doRequest() { makeRequest(url, username, password); } function makeRequest(url, username, password) { var http_request = new XMLHttpRequest(); if (http_request.overrideMimeType) { http_request.overrideMimeType('text/xml'); } if (!http_request) { alert('Cannot create XMLHTTP instance'); return false; } http_request.onreadystatechange = function() { alertContents(http_request); }; http_request.open('GET', url, true, username, password); http_request.send(null); } function alertContents(http_request) { if (http_request.readyState == 4) { if (http_request.status == 200) { if (startOffset == 0) { startOffset = 45; // this value would be extracted from 'http_request' url = encodeURIComponent('https://theapiurl.com/query=' + startOffset); // second call, parameter startOffset has changed doRequest(); } else { } } else { alert('There was a problem with the request.'); } http_request.onreadystatechange = function fnNull(){}; } } </code></pre>
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