javascript JSONP callback function not defined

Question

(
function restoreURL() {
    function turnLongURL(data) {
        window.location = data.url;
    }

    var shortUrl = window.location.href;

    var url = "http://json-longurl.appspot.com/?url=" + shortUrl + "&callback=turnLongURL";

    var script = document.createElement('script');
    script.setAttribute('src', url);

    document.getElementsByTagName('head')[0].appendChild(script); 
})();

code is above, but the firebug told me, turnLongURL is not defined

why is that?

Quentin · Accepted Answer · 2015-03-11T11:05:10.047

8

JSON-P is added to the document using a script element, so the function call inside it has to reference a function that exists in the global scope.

turnLongURL is limited to the scope of restoreURL since it is defined inside it.

Moving the function declaration to the global scope, or changing it to a function statement thus:

window.turnLongURL = function (data) {

… should make it work.

Remember to account for the possibility of race conditions should multiple JSON-P requests be sent out before the first returns.

edited Mar 11 '15 at 11:05

answered Dec 24 '10 at 19:52

Quentin

914,110
126
1,211
1,335

it is still not working, and keep saying turnLongURL is not defined... does it make any difference if i am editing a greasemonkey script? – Ya Zhuang Dec 24 '10 at 19:59
@Quentin What is the best way to account for jsonp race conditions? – David d C e Freitas Dec 01 '11 at 20:55
Related? http://stackoverflow.com/questions/8495825/jsonp-request-in-chrome-extension-callback-function-doesnt-exist – James Hibbard Oct 09 '16 at 18:44

javascript JSONP callback function not defined

1 Answers1