Tranfer data from local variable to global in javascript

Question

I have some problem with transfer of variable outside the function. It's seems to be very simple but I have some problem with it.

var myJson;
var url = "https://openbook.etoro.com/api/Markets/Symbol/?name=" + symbol;
var xhr = (window.XMLHttpRequest ? new XMLHttpRequest() : new ActiveXObject("Microsoft.XMLHTTP"));
xhr.onreadystatechange = XHRhandler;
xhr.open("GET", "proxy.php?url=" + url, true);
xhr.send(null);

function XHRhandler() {

    if (xhr.readyState == 4) {

        var json;
        if (JSON && JSON.parse) {
            json = JSON.parse(xhr.responseText);
        } else {
            eval("var json = " + xhr.responseText);
        }
        console.log(json);
        myJson= json;
        xhr = null;
    }

}
console.log(myJson);

What I need is to pass the data from local variable json to global myJson; But when i do console.log(myJson) i get undefined. What is the problem?

Thank you

It is undefined since `console.log(myJson);` executes immediately without waiting for xhr to complete. XHRhandler will be called only when the data arrived from the server. — Fizer Khan, Mar 12 '14 at 09:33
possible duplicate of [How to return the response from an AJAX call?](http://stackoverflow.com/questions/14220321/how-to-return-the-response-from-an-ajax-call) — Quentin, Mar 12 '14 at 09:42
You can also try `promise` and set variable in its callback. — Mithlesh Kumar, Mar 12 '14 at 12:41

score 0 · Answer 1 · answered Mar 12 '14 at 09:35

0

Try moving the statement console.log(myJson); inside your if condition or alternately initialize your variable with some value. It seems your statement is getting called before it is getting populated with any value.

answered Mar 12 '14 at 09:35

ManeetK

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score 0 · Answer 2 · answered Mar 12 '14 at 09:41

The XMLHttpRequest is async so it is not done yet when you try to write the myJson variable to console. Wrap it in a function and call that function after the XMLHttpRequest is completed instead.

var myJson;
var url = "https://openbook.etoro.com/api/Markets/Symbol/?name=" + symbol;
var xhr = (window.XMLHttpRequest ? new XMLHttpRequest() : new ActiveXObject("Microsoft.XMLHTTP"));
xhr.onreadystatechange = XHRhandler;
xhr.open("GET", "proxy.php?url=" + url, true);
xhr.send(null);

function XHRhandler() {

    if (xhr.readyState == 4) {

        var json;
        if (JSON && JSON.parse) {
            json = JSON.parse(xhr.responseText);
        } else {
            eval("var json = " + xhr.responseText);
        }
        console.log(json);
        myJson= json;
        xhr = null;
        writeToConsole();
    }

}

function writeToConsole() {
    console.log(myJson);
}

Tranfer data from local variable to global in javascript

2 Answers2