Question

Can anyone see the problem with this code? When ‘out’ is returned, it has a value of “”. I have no idea why, perhaps it’s something about the getJSON function im not aware of.

I’m trying to pass a URL to this function, have it perform getJSON on the URL, and add the results (which i’m also formatting) to a text string. I want them all in one text string, so i can parse the string with regex. Any help is appreciated, thanks!

function getSearch(url) {
var out = '';   // output variable

$.getJSON(url, function(data) {
    for(var i = 0; i < numResults; i++) {
        out += '<p class="hash_list">' + '<a href="http://www.twitter.com/' + data.results[i].from_user + '">' + data.results[i].from_user + '</a>: ' + data.results[i].text + '</p>';
    }
});

return out;
}

Answer 1

ajax is asynchronous, the code you have would return before the ajax request has finished.
There are a few ways you can restructure your code.

You can pass in a callback function that gets executed once the request has finished.

function getSearch(url, callback) {
   $.getJSON(url, function(data) {
     var out = '';    
     // btw what is numResults ?? 
     for(var i = 0; i < numResults; i++) {
        out += '<p class="hash_list">' + '<a href="http://www.twitter.com/' + data.results[i].from_user + '">' + data.results[i].from_user + '</a>: ' + data.results[i].text + '</p>';
     }
     if( typeof callback === 'function' ) callback( out ); 
   });
}

Then you would use the function like this.

getSearch('test.php', function(out){ 
   // here you can use the out variable 
}); 

Or you can use jquery deferreds to return a promise and pass the out variable as part of the argument when you resolve the deferred. Here’s an example

function getSearch() 
{    
    var deferred = $.Deferred(); 
    $.getJSON(url, function(data) {
     var out = '';    
     // btw what is numResults ?? 
     for(var i = 0; i < numResults; i++) {
        out += '<p class="hash_list">' + '<a href="http://www.twitter.com/' + data.results[i].from_user + '">' + data.results[i].from_user + '</a>: ' + data.results[i].text + '</p>';
     }
     deferred.resolve( out ); // resolve the request and pass in the out argument.  
   });

    return deferred.promise(); // return a promise 
}


$.when( getSearch() ).then(function( out ){  // the out variable will get passed in
     console.log( out );
});