how do I return text file value Asynchronous in ajax? "Synchronous is getting deprecated"

Question

I Try using the ajax Asynchronous, but the value just return "undefined". No Jquery please!!

function readTextFile(file){
    if(window.XMLHttpRequest) {
        var rawFile = new XMLHttpRequest();
    }else {
        var rawFile = new ActiveXObject("Microsoft.XMLHTTP");
    }

    rawFile.open("GET", file, false);
    rawFile.send(null);

    //alert(rawFile.responseText);
    var textvalue = rawFile.responseText;
    return textvalue;
}


var str = readTextFile(file);

Check this question and the answer to it: [How can I take advantage of callback functions for asynchronous XMLHttpRequest](http://stackoverflow.com/questions/5485495) — t.niese, Mar 25 '16 at 15:26

score 1 · Answer 1 · answered Mar 25 '16 at 15:26

1

Please try this solution:

function readTextFile(file) {
  var xhttp = new XMLHttpRequest();
  xhttp.onreadystatechange = function() {
    if (xhttp.readyState == 4 && xhttp.status == 200) {
        var textvalue = xhttp.responseText;
    }
  };
  xhttp.open("GET", file, true);
  xhttp.send();
}

answered Mar 25 '16 at 15:26

kasynych

50
2

sorry, but nope, that doe even return the textvalue; – toastext Mar 25 '16 at 15:37
@Danny you can't return value from asynchronous call, you need to use callback. – jcubic Mar 25 '16 at 15:39
@jcubic how do I make a callback without jquery with my codes above? I need an example, I'm really lost here. the link provided above by someone that down vote me didn't realize that I said NO J query! – toastext Mar 25 '16 at 15:43
I think you have to use callback – kasynych Mar 25 '16 at 15:58

score 1 · Answer 2 · answered Mar 25 '16 at 15:48

1

You need to use onreadystatechange event and a callback:

function readTextFile(file, callback){
    if(window.XMLHttpRequest) {
        var rawFile = new XMLHttpRequest();
    }else {
        var rawFile = new ActiveXObject("Microsoft.XMLHTTP");
    }
    rawFile.onreadystatechange = function() {
        if (rawFilereadyState == 4 && rawFile.status === 200) {
           callback(rawFile.responseText);
        }
    }
    rawFile.open("GET", file, false);
    rawFile.send(null);
}


readTextFile(file, function(str) {
  // use the str
});

answered Mar 25 '16 at 15:48

jcubic

61,973
54
229
402

Thanks jcubic, but how does the responseText get return so I can put it in a string?(: and which function do I use. Sorry I'm new to the callback function in ajax and all the guide involve jquery.T^T – toastext Mar 25 '16 at 15:54
it's the same as `var str = readTextFile(file)` but the str is inside the callback function as argument, instead of after the readTextFile you put your code inside a callback and use str as argument instead of variable. – jcubic Mar 25 '16 at 16:22

how do I return text file value Asynchronous in ajax? "Synchronous is getting deprecated"

2 Answers2