纯javascript longpolling聊天

Question

So I have started a project, where I want to make an online ajax chat, but I do NOT want to use jQuery JSON, COMET and so on. I am looking for pure javascript, no libraries no framework.

Good news is that I have already made the chat and it is working fine. Why do i make this post? Because I simply cannot find any pure javascript solution for long-polling. Currently I am using the setInterval method to "ask" the database to send whatever is in the database. now, how do I execute my ajax request whenever I get a response? (Long-polling).

please bear in mind that I am not looking for a jQuery solution or what have you.. I am using pure JavaScript and PHP. No framework or library.

Thanks in advance.

Answer 1

i believe this is relatively close to what your looking for - referencing a vanilla js ajax tutorial on nettuts plus:

load('test.txt', function(xhr) { 
    document.getElementById('container').innerHTML = xhr.responseText;  
    // you would obviously custom tailor this peice to utilize your specific data
});  

function load(url, callback) {  
    var xhr;  

    if(typeof XMLHttpRequest !== 'undefined') xhr = new XMLHttpRequest();  
    else {  
        var versions = ["MSXML2.XmlHttp.5.0",   
                        "MSXML2.XmlHttp.4.0",  
                        "MSXML2.XmlHttp.3.0",   
                        "MSXML2.XmlHttp.2.0",  
                        "Microsoft.XmlHttp"]  

         for(var i = 0, len = versions.length; i < len; i++) {  
            try {  
                xhr = new ActiveXObject(versions[i]);  
                break;  
            }  
            catch(e){}  
         } // end for  
    }  

    xhr.onreadystatechange = ensureReadiness;  

    function ensureReadiness() {  
        if(xhr.readyState < 4) {  
            return;  
        }  

        if(xhr.status !== 200) {  
            return;  
        }  

        // all is well    
        if(xhr.readyState === 4) {  
            callback(xhr);  
        }             
    }  

    xhr.open('GET', url, true);  
    xhr.send('');  
}

and you could build your "success" handlers into the 'ensure readiness' based on the return values

heres a link to the nettuts tutorial

and another to the MDN ajax API docs