How can I get jQuery to perform a synchronous, rather than asynchronous, Ajax request?

Solution 1:

From the jQuery documentation: you specify the asynchronous option to be false to get a synchronous Ajax request. Then your callback can set some data before your mother function proceeds.

Here's what your code would look like if changed as suggested:

beforecreate: function (node, targetNode, type, to) {
    jQuery.ajax({
        url: 'http://example.com/catalog/create/' + targetNode.id + '?name=' + encode(to.inp[0].value),
        success: function (result) {
            if (result.isOk == false) alert(result.message);
        },
        async: false
    });
}

Solution 2:

You can put the jQuery's Ajax setup in synchronous mode by calling

jQuery.ajaxSetup({async:false});

And then perform your Ajax calls using jQuery.get( ... );

Then just turning it on again once

jQuery.ajaxSetup({async:true});

I guess it works out the same thing as suggested by @Adam, but it might be helpful to someone that does want to reconfigure their jQuery.get() or jQuery.post() to the more elaborate jQuery.ajax() syntax.

Solution 3:

Excellent solution! I noticed when I tried to implement it that if I returned a value in the success clause, it came back as undefined. I had to store it in a variable and return that variable. This is the method I came up with:

function getWhatever() {
  // strUrl is whatever URL you need to call
  var strUrl = "", strReturn = "";

  jQuery.ajax({
    url: strUrl,
    success: function(html) {
      strReturn = html;
    },
    async:false
  });

  return strReturn;
}

Solution 4:

All of these answers miss the point that doing an Ajax call with async:false will cause the browser to hang until the Ajax request completes. Using a flow control library will solve this problem without hanging up the browser. Here is an example with Frame.js:

beforecreate: function(node,targetNode,type,to) {

    Frame(function(next)){

        jQuery.get('http://example.com/catalog/create/', next);
    });

    Frame(function(next, response)){

        alert(response);
        next();
    });

    Frame.init();
}

Solution 5:

function getURL(url){
    return $.ajax({
        type: "GET",
        url: url,
        cache: false,
        async: false
    }).responseText;
}


//example use
var msg=getURL("message.php");
alert(msg);